TERRY GROSS, HOST:

This is FRESH AIR. I'm Terry Gross. We're going to talk about the hidden world inside our bodies, the remarkable design of our organs, the messages contained in our body fluids, and how things can turn foul when something goes wrong. My guest, Dr. Jonathan Reisman, is an internist, pediatrician and ER physician, and the author of the new book, "The Unseen Body." Each chapter is about a specific body part or body fluid from his perspective as a doctor. So there's chapters on the throat, heart, feces, genitals, liver, brain, skin, urine, blood and so on. It's fascinating material, but I want to acknowledge at the start that our conversation will include discussion of body fluids and genitals. And I know that makes some people uncomfortable or squeamish. I suspect Dr. Reisman will try to convince you that you needn't be squeamish about the complexity of the human body.

Before studying medicine, his passion was studying the natural world and ecology. As a medical student, he found that exploring the body felt similar to exploring the outside world. Each organ was a different creature with its own unique appearance and behaviors. He's practiced medicine in remote and culturally unique regions of the world, including the Arctic, Antarctica, high altitudes in Nepal, people living on the street in Calcutta, in India, and among the Oglala Sioux in South Dakota. He currently works in several ERs in the Philadelphia area.

Dr. Jonathan Reisman, welcome to FRESH AIR. It's a fascinating book. I know you're fascinated by our insides, our organs, our body fluids. It's part of what drew you to medicine. But many people are squeamish about looking even at a video of a chest cut open during surgery. Why do you think that the body can seem so revolting or upsetting?

JONATHAN REISMAN: Well, thanks so much for having me here today, Terry. I think that a lot of people are simply, you know, grossed out or repulsed by what they're not used to. You know, when we go about our daily lives, we don't see the body's innards. We don't see our internal organs. And we try to do our best to try not to see the, you know, the excreted bodily fluids that come out of us too. Just our normal daily life does not involve seeing those deeper parts of the body. And part of the reason I named my book "The Unseen Body" is because I'm trying to open up, you know, that unseen portion of the body that we all don't see in our daily lives, pull back the curtain, if you will, on how all the organs work, how fascinating they are, but also how they impact every aspect of our lives from daily life and, you know, all the milestones of our lives from birth to death and beyond.

GROSS: The first time you could open a cadaver as a medical student, did you find it revolting or fascinating?

REISMAN: I actually found it absolutely fascinating on that first day. In fact, before the end of the very first day of medical school, during which they had us start in the anatomy lab, which is the class in which we would dissect the cadaver over the coming months, before the end of the very first day of medical school, I decided that, when I died, I would want to donate my body for the same medical school dissection, you know, the same thing that was happening between me and the three other medical students that shared this cadaver, you know, kind of exploring its innards and sort of seeing what's inside this strange man that we never knew in life. And, you know, as an extension, when you look inside the body of another person, you're necessarily looking inside your own, seeing how you are built, how organs are, you know, organized inside of you. And so it kind of takes on this very self-reflective and philosophical nature. And I was really taken with that from Day 1 and resolved - and I'm still sticking to it - when I die, I want to donate my body for medical student dissection.

GROSS: Well, let's start talking about a part of the body that does not make people squeamish. I'm thinking of the throat. When you were in med school, you were amazed at how stupidly designed the throat seemed. What seemed stupid about it?

REISMAN: You know, what is its basic function? The throat helps us deal with whatever enters our body, you know, usually through the mouth. We drink. We eat. We inhale. Air comes in through the mouth and the nose. All of it ends up in the throat. And it's the throat's very, very important job to deal with all of it. Specifically, the throat has to take food, drink saliva, other things that we mean to swallow and make sure they go into the one tube, the esophagus, the food tube, which goes down to the stomach. The tube right next to the esophagus, literally millimeters away, is the windpipe, which goes down to the lungs. And every single time something passes through the throat, its most important job is to make sure that that - whatever it is besides air does not go down the windpipe.

This - the design seemed fairly stupid to me because if you mess up just once, if you try to talk while swallowing just once or laugh with your mouth full, as we all know, sadly, you know, you can aspirate, choke and die just from one little slip up. So it seemed sort of silly to have these two tubes right next to each other. And every time we swallow food and drink or every time we thoughtlessly swallow our own saliva, which happens basically all day, every day of our lives, that material comes within a few millimeters of slipping into the windpipe, therefore a few millimeters within killing us.

And so it seemed like such a really poor design. Like, maybe food and drink and air could enter the body through different orifices. Of course, it can't because of how we form in the womb. But it seems like a big problem that can cause a lot of trouble, and especially in contrast to other parts of the body, which seemed so exquisitely designed, so brilliantly constructed to keep us alive, to ensure our survival. The throat almost seemed like a really easy way to die.

GROSS: So, to make matters even worse, for people who are older and have weaker swallowing muscles or who have any kind of like dementia or illness that weakens those muscles, it's so easy to choke on food and have it go down the windpipe instead of down the esophagus. And that leads to aspirational pneumonia. Would you describe what that is?

REISMAN: Sure. And, you know, any pneumonia is an infection in the lungs. Aspiration pneumonia in particular is a specific kind caused by aspirating food or drink or saliva into the wrong tube, into the windpipe. You know, the throat is so dangerously designed. And to top off all of its dangers, the No. 1 strain of pneumonia causing bacteria in the world lives in our throats right above the entrance to the lungs. And so one small mishap, one little bit of food or saliva can go down there. It can drag those bacteria with it, and that can turn into a pneumonia, which is a very common problem for the elderly and infirm.

GROSS: Yeah. And I'm sure you've had a lot of patients who've gone in and out of the hospital because they choke easily on food and get aspirational pneumonia, recover, go home, choke again, go back to the hospital and so on. You say that you came to see pneumonia as an escape hatch for the body at the end of life. Can you talk about that?

REISMAN: I tell the story of Suzanne (ph), who bounced back to the hospital again and again with aspiration pneumonia. And, you know, her end-of-life-experience, she ended up dying of that second bout in the hospital, she had made it clear in her living will that she didn't want extraordinary measures. She didn't want to be on a ventilator. And all of her family agreed. And so it sort of gave me this different perspective. It was actually for me as a young doctor one of the most tension-free end-of-life experiences of a patient that I had had. These can often be very stressful with a lot of family tensions that are once hidden coming to the fore. But in this case, everyone agreed it was all very peaceful, almost, even though it was sad.

But, you know, the aspiration pneumonia came to be seen by me as a way out when your quality of life tends to ebb. You know, when you have dementia and you can no longer think, no longer talk or no longer recognize your loved ones, your throat isn't working properly, and you tend to aspirate. And then aspiration pneumonia that results can almost be a way out from a degraded existence. And while it's never my place to determine when someone's quality of life is too low for them to continue living, this is a recurrent problem that does happen to the old and infirm. And it used to be called old man's friend. So aspiration pneumonia was called this because it often does provide this end - a dignified end to prolonged suffering and illness.

GROSS: Well, let's take a short break here. Then we'll talk some more. If you're just joining us, my guest is Dr. Jonathan Reisman, author of the new book "The Unseen Body." We'll be right back. This is FRESH AIR.

(SOUNDBITE OF LOOP 2.4.3'S "ZODIAC DUST")

GROSS: This is FRESH AIR. Let's get back to my interview with Dr. Jonathan Reisman, a doctor of internal medicine, pediatrics and emergency medicine. His new book is called "The Unseen Body: A Doctor's Journey Through The Hidden Wonders Of Human Anatomy."

So before I ask you the next couple of questions, I want to tell our listeners that if you're squeamish about medical discussions of body fluids, these next few questions might not be for you. On the other hand, what Dr. Reisman has to say may make you more interested in how your body works and make you less uncomfortable with the jobs it has to perform.

So another example of unusual design that can lead to problems is the parts of our body responsible for urination, defecation and sexual pleasure and, for women, giving birth are all crammed together in this one little region. And that's one of the reasons women get UTIs. What do you see as a doctor when you look at the design?

REISMAN: Right. So actually, it makes me think of the same design pattern and reasons for why the esophagus and the windpipe are so dangerously close to each other. You know, basically, all of us started out as a microscopic - a fertilized ovum. But after that, we grew into a small flat disk that then rolls itself into a little tube. And as we grow in the womb and then grow, you know, outside the womb after birth, we basically become a more and more complicated tube, but we do retain that basic structure, that basic blueprint for the body. And so the tube has an entrance at the top where food, drink, saliva and air also come in, and that tube divides into the windpipe and esophagus, creating all the aspiration-related problems we talked about.

At the other end, all the exits - you know, they start out as one exit, and then they divide into basically two holes in men, three holes in women. And it does cause, you know, problems like you're talking about - urinary tract infection, where bacteria from the one exit of the anus can get close to the urethra and get into the bladder and cause that infection. It's just one of the downsides of the human body's design that you have to deal with on a day-to-day basis as a doctor.

GROSS: Were you initially uncomfortable dealing with the genital area, including the anus, because of its sexual aspects or just because of, like, the yuck aspects of defecation?

REISMAN: I would say I had less of a problem with kind of the yuck aspects of it since I probably stopped maturing at 13 year old...

GROSS: (Laughter).

REISMAN: ...At 13 years old, like most men. But I would say it was more the social aspects that were difficult. You know, when you start training to be a doctor, you end up talking about everything from sex to defecation with complete strangers who you met just a moment before. And so often, you know, in the presence of someone who maybe resembles my own grandmother, you know, bringing up these topics can make you feel very uncomfortable since they're topics you'd never bring up to most people that you meet in daily life. But that's one of the most amazing things about medicine, is you meet these strangers, and a second later, you're hearing from them about their deepest, darkest, most personal, you know, secrets, aspects of their life, what's stressing them out, what's worrying them. And so that, unfortunately or fortunately, has to include the grosser aspects of what it means to live in a human body.

GROSS: You actually have a favorite body fluid. What is special about urine to you as a doctor?

REISMAN: So urine has a unique place among bodily fluids. You know, most of a doctor's job is interpreting bodily fluids - you know, testing them, sending them to the lab to gather data to figure out what is wrong with a patient, what's the cause of their symptoms or the sign of disease or the pain. But I find that as a doctor, urine really has this broad array of messages it can tell me about my patients. You know, every bodily fluid is a language, and it speaks to doctors. And if we can interpret its messages, we can hear what it's telling us about what's wrong with the patient.

Urine is kind of the perfect example of this and provides such a wealth of information. You know, for instance, take the color. Red urine can tell me that a patient perhaps has a kidney stone. Perhaps they have a urinary tract infection. Perhaps they have a tumor on their kidney or on their bladder. In that way, the red color is telling me the possibilities of what could be afflicting this patient. But urine has this ability to tell you about the entire body, not just the urinary tract through which it flows and comes out of the body. You know, so the same red urine, for instance, could be telling me about muscle breakdown, which can turn the urine red. It could be telling me about a problem with red blood cells, all these things that are kind of unrelated to the kidneys and urinary tract themselves.

And even, for instance, with diabetes, you know, we end up - it often presents because people urinate a lot. So there's no obvious connection between the pancreas, where the problem is located, with diabetes Type I. Yet we can find these clues in the urine, and then we often test the urine itself for various chemicals that can tell us about the pancreas and its failing to make enough insulin. So in that way, urine is sort of this crystal ball where you can sort of divine all these unrelated things about the body as a whole.

GROSS: You work with a lot of people living on the street in India, in Kolkata. So a lot of patients - I mean, those patients were obviously very poor. I think there's a lot of diarrhea in living conditions like that. You even picked up some of that yourself while you were living there. Diarrhea in children can lead to fatal dehydration if not treated. What were some of the clues you looked for in patients' stool in India, dealing with patients living on the street, to learn more about what their problem was and whether it was a serious problem or not?

REISMAN: So just like other bodily fluids can give messages to a doctor to figure out what's going on, stool is another one, and we interpret it in similar ways. So when someone has diarrhea, you know, which - a term that can really vary quite differently in different people. So it's important to understand what a person's, you know, baseline stooling pattern is before saying that they are - either have diarrhea or constipation.

But in India, I did see a lot of diarrhea. And diarrhea actually remains one of the most important causes of death in children under 5 in much of the world, which is quite shocking. Here in the U.S. - you know, as a pediatrics resident in Boston, I treated a lot of kids with diarrhea and never saw any of them get very sick. Some simple IV fluids, you know, fixed them, and they went home a few days later. But in India, it's a much bigger problem. IV fluids are harder to come by. Even oral rehydration solution, which could help a lot of children, is not always readily available.

But you know, we look for similar things in anyone with diarrhea, whether in India or here. We look for the presence of blood, the presence of fever, sometimes the presence of mucus. Certain colors in the stool can tell us certain things about what - which bacteria might be causing it, whether it's bacterial or viral or caused by amoeba.

GROSS: In the U.S., a really bad problem related to diarrhea is C. diff, which is usually a hospital- or nursing home-acquired infection that leads to very severe and uncontrollable diarrhea that can really lead to death if it's either untreated or if the treatment doesn't work. And the treatment is often antibiotics, but that doesn't always work. And even if it does, the C. diff can come back. And one of the treatments being used now, I think on a pretty experimental basis, is fecal transplants. And we've talked about this before on the show, but it sounds like you've dealt with it directly. So let's start with describing what that is and why it seems like a promising treatment.

REISMAN: So fecal material transplant - or FMT, or just fecal transplant - is a new, experimental modality where basically you take the stool from one person's colon and with it comes all these species of bacteria, fungus, virus, even some parasites. All of these different creatures live inside of all of us, and that's normal. And we, in some ways, depend on them for health to an extent that, you know, we had not known until recent decades.

And specifically, the C. diff diarrhea is caused by - most commonly, a doctor will prescribe a patient antibiotics for an infection, and while they do kill that microbe causing the infection, they have the, you know, unintended side effect of killing much of the normal, healthy, desirable microbes that live in our colon. It's sort of like there's this empty ecological niche now in this person's colon, and bacteria that take advantage of it include C. diff, or Clostridium difficile. And C. diff tends to proliferate in this now empty - you know, more empty colon and can really cause severe diarrhea. As you said, it can lead to death, or it can lead to the need to surgically remove the colon entirely.

So it makes perfect sense. If someone is suffering from C. diff because their normal, healthy microbes were decimated by antibiotics, take those normal, healthy microbes from someone else who has them in - you know, in large numbers in their colon. Take it from that person, and put it into the recipient's colon. And this treatment is experimental, though it's more or less accepted these days 'cause many studies have shown that the cure rate is better than antibiotics, which is the only other treatment we have besides surgical removal of the colon. So it's very promising, and people theorize it could be useful in many other areas of health and disease as well.

GROSS: You describe the fecal matter being put in a capsule and swallowed. And I thought, how can that be? We've all been taught at such a young age that you never, ever let anything that's touched fecal matter near your mouth. So how come it's OK to actually swallow it in a capsule?

REISMAN: So this is a very good question. And, you know, in the early days of fecal transplants, it was often delivered during a colonoscopy, where the liquid stool was sort of just placed in the colon while you're there during a colonoscopy. But it's been, you know, made more easy to deliver in the form of pills. And you're absolutely right. You know, one of the biggest discoveries of the 19th and early 20th century is that these microbes are killing us and that, specifically, diarrheal disease is spread by someone else's infectious stool making it into the water or food supply. And it's exactly that - getting someone else's stool into your intestines that's causing all these children in poor countries like India to die before their 5th birthday.

And yet, you know, this tenet of germ theory that we've clung to so strongly turns out to be completely overturned by this fecal transplant, which is an accepted treatment. And it is surprising. I call it the most iconoclastic treatment in all of medicine 'cause it basically overturns our most cherished ideas that kind of created modern medicine, the understanding of microbes and how they infect and kill us.

GROSS: Let's take a short break here. If you're just joining us, my guest is Dr. Jonathan Reisman. He's the author of the new book "The Unseen Body." We'll be right back. I'm Terry Gross, and this is FRESH AIR.

(SOUNDBITE OF HOWARD SHORE'S "MAIN TITLE")

GROSS: This is FRESH AIR. I'm Terry Gross. Let's get back to my interview with Dr. Jonathan Reisman, author of the new book "The Unseen Body." It's about the insides of our bodies, the remarkable design of our organs, the messages contained in our body fluids and how things turn foul when something goes wrong. Each chapter is about a specific organ or body fluid from his perspective as a doctor. He's an internist, pediatrician and ER physician who's practiced medicine in remote regions and unique cultures, including the Arctic, high altitudes in Nepal, urban slums in Calcutta, India, and among the Oglala Sioux in South Dakota. He currently works in several emergency rooms in the Philadelphia area.

You've had some very obese patients. And you say that your obese patients needlessly suffered. What are some of the messages you took away from that experience?

REISMAN: One of the messages that was shouted at me is just that our health care system is not designed for the biggest people. And I think overweight and obese people know that very well. Every time they go to the doctor's office, maybe the blood pressure cuff isn't big enough. Maybe the chairs in the waiting room aren't big enough, you know? Every aspect of our care is not set up for this really growing portion of our population. And so it's a real deficiency.

But it also brings up questions of, you know, what weight should we make things, you know, fit to? How high should the bed in a CAT scanner go in terms of the weight it can tolerate, you know? How wide should our wheelchairs be? And how much weight should crutches be able to take when someone sprains ankle, you know? These are all questions that we don't really have the answer to. But, you know, a large proportion of modern humans are overweight and of a certain size. And we need to accept that fact, I think, and make sure that they're getting care.

GROSS: You quote the head of the Massachusetts General Hospital Obesity, Metabolism and Nutrition Institute. And he basically says that we call obesity a disease, but we treated differently than all other diseases. Doctors tend to see it as a patient's failure rather than a disease. In what sense do you think of it as a disease? And what are the implications of that for treating it?

REISMAN: I compare it to addiction, actually, in the book, where in recent years, I think doctors have finally and begrudgingly come around to seeing addiction as sort of this combination of, you know, a person's will to do what they want and to make their own choices, sometimes bad choices - but also, the disease aspect is where there's this propensity to do that due to genetics, due to, you know, that person's brain and the individual structure and chemical makeup of the brain, not to mention past traumas in life, which tend to make people, you know, more prone to using substances to alleviate the kind of bad memories and other bad experiences they're having. I think that we've finally come to see addiction as this - as a disease. We're being constantly encouraged to treat addiction, especially because of the opioid epidemic, you know, ravaging our society.

I think there has not yet been that realization or that shift in treating obesity as a disease. There's surgery, of course, you know, bypass and other gastric surgeries that help people lose weight and are quite successful. There are actually now many medications that can also help people who are overweight and obese. As Dr. Kaplan said when I talked to him for the book, these medicines are woefully underused by primary care doctors. And he believes that it's because doctors don't see obesity as a disease, which is probably something we need to start doing, you know? All the other aspects of modern life, all the other deleterious effects on human physiology that we experience living our modern lifestyles - like kidney disease, high blood pressure, elevated cholesterol - these are all factors that we can treat. And there's many medicines on the market for doctors to choose from to treat their patients. But obesity is sort of seen as different. It's not seen as just an outgrowth of modern life. But it's seen as a personal failing. And I think we have to change that.

GROSS: One of the many things you've done in medicine is work as a hospitalist. So what's your diagnosis of hospitals and the ways that they are not suited to regaining health?

REISMAN: Oh, the list is very long. You know, sleep loss among the sick is an epidemic in hospitals these days, you know? Everyone's losing sleep. No one's sleeping well, partly because of stress and our smartphones and other screens. But in the hospital, too, there's just this constant barrage of noise and alarms going off and light coming in through the windows. And it's very hard to sleep in hospitals. And that's one of their big downsides that would be improved on if people were still at home.

GROSS: Yeah. You say you used to wake up patients to, like, you know, check their vitals and talk with them. And with terminal patients now, you won't do that anymore.

REISMAN: That's right, when I was training and I had a long list of patients. And I was still very inefficient with my movements, my rounding, where I saw each patient one by one in the morning before I had to meet with an attending physician and kind of describe what I planned to do for that patient that day. And so I often, in a rush in the morning, woke up one patient after the other. I often felt terrible about it. I would hesitate to do it. But sort of the pressure of residency, the pressure pushing me towards having all my plans ready and all my notes written by the time I would talk to my attending, sort of, you know, put me - sort of forced me to do it. I don't want to take any blame away from myself. I am one of those health care workers who wake people up needlessly while they're trying to get their restful sleep in the hospital.

I describe in the book one patient in particular who I had as a resident. He was suffering from terminal gastric cancer. And he was very young, just in his 30s. And every day on rounds, I woke him up in the morning even though I felt horrible about it, even more horrible than usual because I knew his case was terminal. There was an oncologist sort of overseeing me and sort of making the larger decisions about treatment and how to manage the cancer. But I was the one sort of examining him each day, writing for his IV fluids, repleting all his electrolytes, which were depleted because of poor diet and the toxic chemo treatments he was getting. And so waking him up in the morning felt especially egregious because I felt like I was sort of waking him up back to the reality of his terminal cancer, you know, instead of letting him sleep more and maybe dream of healthful, long life.

I was waking him up and almost re-diagnosing him every morning by bringing him back to reality and saying, you know, here you are, back in the hospital. It was not a bad dream. And, you know, you're - don't have many weeks to live. And so from that moment on, I had sort of decided for myself, for the terminally ill, unless it was absolutely necessary, I made a rule for myself as a hospitalist that I would never wake someone up again.

GROSS: Let me reintroduce you here. If you're just joining us, my guest is Dr. Jonathan Reisman, author of the new book "The Unseen Body." We'll be right back. This is FRESH AIR.

(SOUNDBITE OF PAQUITO D'RIVERA'S "CONTRADANZA")

GROSS: This is FRESH AIR. Let's get back to my interview with Dr. Jonathan Reisman, a doctor of internal medicine, pediatrics and emergency medicine. His new book is called "The Unseen Body: A Doctor's Journey Through The Hidden Wonders Of Human Anatomy."

You worked with patients who had liver disease hoping for a liver transplant, and you saw the fluids that build up in the body with that disease and cause a lot of pain for the person who has it. And even when you aspirate the fluid, it tends to build up again. So reading the liver chapter in your book, I thought, this doctor is never going to eat liver again. And it was actually the opposite. You hated liver, and you started eating it after attending to patients who had liver disease. Can you explain that?

REISMAN: Terry, my journey to kind of become what we might call a foodie began in medical school, which is the opposite of what anyone would expect, specifically began in the class anatomy lab where I was dissecting the cadaver. You'd think that would be where people go to lose their appetite completely. But for me, it was the opposite. There was a professor, actually, who really enjoyed pointing out which of the human muscles we were learning corresponded to which cuts of beef that we might have heard of. So for instance, you know, the infra spinatus muscle of the shoulder corresponds to the flat iron steak, and psoas major muscle inside our abdomens correspond to the filet mignon. And we learned about which muscles of the thigh correspond to the top round and bottom round and eye of round, et cetera.

And I realized that the same knowledge that goes into understanding the human body, how muscles are shaped, how they connect to bone, help us move, how tendons, ligaments and joints are all, you know, structured together, how they're designed, that's the same knowledge that a butcher might use to effectively butcher an animal, to to get that certain cuts of meat to be in their optimal state for cooking. And so I found that there was a lot of overlap in knowledge that would help me as a doctor and help me learn to butcher. And I actually did - in that first semester of anatomy lab, I went to a slaughterhouse to see how they, you know, operate, how they turn these bodies into meat. And the liver in particular was an interesting case because I always thought it was absolutely gross when I was growing up. Chopped liver was often around on holidays, and everyone in my family loved it. I thought it was repulsive - the taste, the appearance, the smell.

But after medical school, after I learned kind of a mind-boggling amount about the liver, how it functions on the microscopic level, the cellular level, how it works inside of us, and it's connected to our other organs, I couldn't quite get over the fact that that incredibly complex biological entity of the liver that keeps us healthy our entire lives is the exact same thing that goes into chopped liver and gets spread on crackers, you know, on my family's holidays. I couldn't quite get over that. And I thought how sort of magical the transformation was from this living, incredibly complex organ to food. And so it kind of spurred me to try it again. And I slowly got used to it. And now I love liver.

GROSS: So as you say, you went to a slaughterhouse. It was a kosher slaughterhouse. And you were learning there about the barrier between the outside and the inside of the body. Can you tell us what you learned?

REISMAN: I had sought out a slaughterhouse. I actually didn't know it was kosher until I got there. I noticed there was a group of rabbis looking at the animal's lungs. And so I realized this was a kosher slaughterhouse, which at first didn't make any difference. But as I spoke to one of the rabbis about how - what exactly they were doing kind of highlighted this important principle of anatomy for me. So basically, they basically look at the lungs in particular. And what they're looking at is to see how much disease those lungs have experienced during the animal's life. So if the animal's had multiple bouts of severe pneumonia, which are visible on the lungs in the form of these fibrous scars that kind of scar the lung to the inside of the chest cavity, the more pneumonia that the animal suffered, the less kosher the entire animal's body gets.

So reading the lungs can tell you about the meat on their, you know, hamstring. But the ultimate test was when they blew up the lungs with air and then looked to see if any of that air was sneaking out through these scars on the surface of the lungs. So they pooled water in their hands and held it over the scars to see if bubbles would come up through it, just like when you have a maybe flat tire and a person is looking for where the air is coming out, you use water to see where it's bubbling through. And what that would tell them is that this animal was sort of violated, right? The external world, which comes into our body through the lungs in the form of the atmosphere that we inhale, it's not really inside our bodies until it crosses that membrane. It can be deep in our alveoli, deep in our lungs. And it's still not inside the body until it diffuses across the lining of the lungs and into the bloodstream.

And so if air was indeed coming out through that scar, it kind of told them that this very important and secret outline of the body that keeps the outside out and the inside in had been violated, and therefore the animal was not kosher at all. And so that taught me something about this membrane that we have underlying all of our bodies, tissues called the basement membrane that sort of creates this outline, this sacred barrier between the inside and the outside.

GROSS: Now, in keeping with this idea, this idea that you've connected medicine with expanding your taste in food, you actually have collaborated with a chef named Ari Miller on something called Anatomy Eats, in which my understanding is you take people to a dinner and the chef explains the food. And you explain what?

REISMAN: So for each dinner, we concentrate on one of the bodily systems. For instance, we held a cardiovascular system dinner where all the main ingredients in the dishes came from the cardiovascular system. So we served three species of heart, cooked in three different ways. We served blood cookies and blood sausage. And we served bone marrow. And for each of those body parts, I describe how that body part works, how it functions in us, in health and disease. You know, both us and the animals, we have similar and analogous body parts that work roughly similar. And so the goal is to sort of draw the attendees to these dinners, draw their attention to how their own body is working, and to see how that function, that anatomy and that physiology comes into the food as as it is prepared from the same body part.

So, you know, I showed them the heart. We cut it open. And I showed them where the coronary arteries are and all the valves and how blood surges through the heart in this way and that. And sort of while they're eating, the conversation continues about their own heart. And in that way, it's sort of a deeper perspective on the food. You know, everyone wants to know sort of more about their food. They want to be more connected to their food these days and know how it's raised and under what conditions and make sure that it was, you know, kind of healthful. And for me, the same thing goes for body parts, you know, understanding how these body parts function in us but also in the animals that we eat, knowing how they function in life and how the anatomy and physiology can be translated into butchering well and preparing well. For me, that creates a deeper connection with the food that I want to have, and so we try to share that with our attendees.

GROSS: So what do your vegan friends think of your collaboration with the chef in which you show the raw organs, talk about the muscles and the blood and everything and then cook it and serve it?

REISMAN: Well, you know, they're not always thrilled about it, naturally, understandably. But I think that actually someone like me who wants to know every dirty truth about the food I'm eating - I don't want anything hidden, you know, I don't want meat showing up as this disembodied red slice in the saran wrap in the grocery store. I want to know exactly where it came from and how it worked in life - that perspective and the vegan perspective I think are closer to each other than people who maybe eat meat but don't want to know the truth, you know, want to hide from their own consciousness the fact that this liver, you know, was in an animal's abdomen before it came to be spread on a cracker on your plate. I think, you know, people who want to know about where food comes from are similar, and they might decide to not eat it because it where of where it comes from or they might decide to excitedly eat it more because of where it comes from. So I think the desire to know where food comes from is what makes people who go to anatomy eats dinners and vegans more similar than they might appear.

GROSS: So I know you plan to donate your body to science, which was a decision you made when you were a medical student after cutting open your first cadaver. What is the process like when you do that? I know how to say that you want it donated, but then what happens? And then what happens to the remains of your body after it's donated to science?

REISMAN: It depends on what you want your body to go to. So in my case, I want to donate my body for medical school dissection as I experienced from the first day of med school. So actually, in that case, you actually contact medical schools themselves and you donate your body to an individual med school, and then they help with the - kind of the arrangements after that. And, you know, once - it took about four or five months for us to dissect our cadavers. And, you know, once we had really looked through the entire body - and the person's looked like a shell of their former selves for sure - after that, they're actually cremated. And we had a ceremony at our medical school where we kind of honored these people who we never met and knew nothing about, you know, who donated their bodies so that we can learn. And still to this day, that - what I saw inside that man's body is, you know, still what I use to kind of understand what's going on inside of all of my patients and my own body. So it was a very archetypal experience.

GROSS: Well. Dr. Jonathan Reisman, a pleasure to talk with you. Thank you so much.

REISMAN: It's been an honor.

GROSS: Dr. Jonathan Reisman is the author of the new book "The Unseen Body." After we take a short break, jazz critic Kevin Whitehead will remember trumpet player and bandleader Ron Miles. He died last week at age 58. This is FRESH AIR.

(SOUNDBITE OF GOMEZ SONG, "BUENA VISTA") Transcript provided by NPR, Copyright NPR.