DON'T USE COSTANZO
Linda S. Costanzo, Ph.D.
Professor Emerita of Physiology and Biophysics
and
Cellular, Molecular, and Genetic Medicine
Virginia Commonwealth University School of Medicine
Richmond, VA 23298
(804) 380-9597
lcostanz@vcu.edu
Advances in Physiology Education 50: 1106-1109, 2026
Every year, my medical students conduct an informal survey that asks: What's your advice for the next class? Students reply anonymously, and their responses are emailed to the medical school faculty and student body. One year, a student wrote, "DON'T USE COSTANZO. IT'S A WASTE OF TIME."
"Costanzo" refers to my physiology textbook (1), now in its 8th edition (2).
From the start, I've welcomed all feedback, positive or negative. Over the years, some of the book feedback has been critical. But this felt different, disproportionate. This felt personal.
I was crushed and humiliated. I wanted to scream and fire back. I wanted to expose the student's unkindness and bring him to his knees. (I thought of the student as "him.") I wanted to rip off the cover of anonymity so all would know who had been so cruel.
But of course I did none of those things. Instead, I closed my eyes, settled my breathing, and started the process of moving on -- meaning I let the episode stew for a decade or two.
I've always been a "book person." In every college and graduate school course, I was the type of student who bought the textbook. I liked the steady support of books and, because I owned them, could mark them up at will -- questions, drawings, summaries, and funny commentaries. To the horror of some, I dog-eared critical pages. I wore out my books!
In the fall of 1967, my junior year as a chemistry major at Duke, I took Qualitative Organic Chemistry. The structure of the course was simple: at the beginning of the semester, each student was given a different unknown organic compound that was to be correctly identified by December. The sine qua non of Qualitative Organic Chemistry was the book -- The Systematic Identification of Organic Compounds, 5th edition, or TSIOC (3). Of course, I bought TSIOC from the campus bookstore -- $6.25, pre-owned by a certain John K. It's now moved with me seven times and, 58 years later, is still on my bookshelf. It's a no-frills, marked up, dog-eared, reliable book that I'm proud to own -- not because I might need to look up organic chemistry tidbits as a physiologist, but because it was this chem major's lifeline. It was the key to learning the hardest of the hard, building blocks to a future I hadn't imagined. When I open the book now, it still smells of "Old Chem" on Duke's West Campus -- like rotting bananas from ester solvents.
The most important word in TSIOC's title is "systematic." The book takes the student, step by step, through the orderly logic of an elimination process. It explains how you can start with a jar of who-knows-what and nail the exact identity of your compound by the end of the semester. An overview chapter explains that you'll start with physical characteristics and ignition tests, then move to melting point determination, then analysis of elements (the biggies like nitrogen, sulfur, iodine, bromine, chlorine), then solubility in neutral, basic, and acidic solutions, then tests for functional groups, then infrared spectroscopy and nuclear magnetic resonance. If you make it that far, the final proof is the synthesis of derivatives. Each phase has a chapter devoted to methods, theories of the methods, explanations of the "whys," and encouraging words of support as students grope in the dark.
The last day of the course was the big reveal. We students gathered, TSIOCs in hand, to receive an envelope with the name of our unknown compound. Either you'd identified your compound correctly per the systematic method or you hadn't. For me and most of my classmates, the semester's work had thankfully paid off, with homage to our treasured TSIOCs.
I'm curious, Mr. ALL-CAPS-doctor-to-be. Have you ever loved a book like that?
Many years after TSIOC, I envisioned writing a didactic medical physiology textbook. Physiology (later Costanzo Physiology) would be written to students and for students. It would understand who students were and what they needed, similar to what TSIOC had done for me in qualitative organic chemistry. Like TSIOC, it would be systematic, stepwise, logical. It would assure students that, "You are not alone, you can get this, I'm with you until the end of the ride. It will be a ride that challenges you, thrills you, and grows your physiology confidence. Welcome aboard!"
At the time of my envisioning, I'd been teaching physiology to medical students for almost 20 years. I had a front row seat to what caused confusion and what switched on the lightbulbs of "aha." I heard students complain that traditional textbooks were strong on facts but often didn't make the connections they needed. They wanted less minutiae and more explanation. They were frustrated by gaps in logic and begged to have those gaps filled.
If I was going to write a textbook, it had to be different. It had to teach physiology just as I teach students in my classroom.
I've noticed that my teaching brain has an interesting feature. When there's a physiology conundrum to resolve, my brain automatically flips into "mind of the student" mode. As if I'm an unofficial student-mind reader. Once I've grappled with the points of missing logic myself, then I can teach others. My book would work the same way for student readers. It would be peppered with "you may wonder why" and "this may seem confusing" (just at the points when student are indeed wondering why or feeling confused) and then go on to give, step-by-step explanations that any student could understand.
Take the example of turbulent blood flow through cardiac valves that are narrowed by atherosclerosis. The turbulence causes murmurs (sounds) that can be detected on auscultation. So far, so good, you say. What's the problem? The problem is that the physiology equation predicting turbulence says that the diameter of the opening is in the numerator; in other words, the bigger the opening, the greater the turbulence (2, p. 129)[1]. That's backwards! Some medical students memorize the turbulence equation without batting an eye. Others decide there are bigger fish to fry in the vastness of medical education. A few others are troubled enough to ask a professor, who either hand-waves over the question or agrees it's confusing. Finally, a small group can't move on until they resolve the seeming contradiction.
My commitment in Costanzo Physiology is to not let these things go. The equation can't be wrong, but murmurs aren't wrong either. After a few restless nights, the "answer" came to me. I whooped and hollered over an "aha" that I could pass along to my student-readers. It boils down to a funny twist in the math, and it was just a matter of explaining that twist. Most students, even those who memorize and move on, are relieved to have the dilemma solved.
The creation of Costanzo's Physiology began one spring day after months of discussion with W.B. Saunders. The acquisitions editor called and simply asked, "Shall we?"
I liked the company I'd be keeping at W.B. Saunders. They'd published landmark books in medical education -- Cecil's Internal Medicine, Robbins Pathologic Basis of Disease, and Guyton's Textbook of Medical Physiology -- all serious books with serious authors, who respect their student-readers.
A countdown clock started when I signed the contract in 1995. Costanzo's Physiology would be substantial -- approximately 500 pages, one million words, 350 figures, 100 tables, and 100 clinical boxes. I was to deliver a final draft of manuscript and figures in 24 months.
Apparently one begins writing the first edition of a physiology textbook by staring at a blank computer screen, frozen, all knowledge vanished into thin air.
I had to pull myself together. Anything related to the book would do. On the blank screen, I typed the titles of ten chapters, with the obvious names of the organ systems. Cellular Physiology, Autonomic Physiology, Neurophysiology, and so on.
Chapter 1. Cellular Physiology.
There, I'd broken the ice. But then what?
The elephant in the room was the substance of the book, which had to be created from scratch. I needed to draft the entire text, tables, figures, sample problems, practice questions, and clinical boxes that would teach all of physiology. Twenty-four months would go fast.
The biggest challenge was filling gaps in my own physiology knowledge by reading reference books and articles. When I hit mind-bending questions such as ‘Why does venous return of blood to the heart have a negative slope?’ or ‘How does the stria vascularis of the inner ear reverse its ionic gradients?’, my work slowed to a snail's pace. I had to decipher how it works for myself before I could explain it clearly to my student-readers.
I committed to writing 1,500 new words each day, six days per week, usually in the evenings. They didn't need to be good words at first, they just needed to be words. When I hit 1500 words for the day, I stopped, ideally in the middle of a sentence (so that I'd have a funny story to tell). Per my calculations, that pace would get me to a million words in 24 months.
I started each day by revising and improving the chapter's earlier material. Then I researched, organized, and wrote the next 1500 words. The work-load steadily increased over the course of each chapter's development, as the to-be-revised sections grew.
My office looked like a physiology war room. Every surface was covered with stacks of books and articles flung open to key passages, coded as "essential," "important," "maybe," "nice, but not essential for students," or "still need to figure this out." Discarded drafts were piled on the floor in a system understood only by me -- I never knew when an early draft might need to be resuscitated.
When a chapter was in decent shape, I mailed the manuscript to my editor for feedback and the figures to a medical illustrator for professional rendering. Their work came back to me as I was creating the next chapters. On and on it went, in overlapping cycles, with each chapter at a different stage of development, until I made it through all 10 chapters.
The possibility of errors (mine!) was a dark cloud over the entire process. I worried about botching a complicated mechanism or missing a critical physiology breakthrough or omitting a step in a calculation. I compulsively checked and re-checked everything, picturing the students who would be counting on me.
You'd think that spotting an error would be a relief. But every near-miss reminded me that others may have slipped under the radar. Every found-error multiplied my dread.
The search for errors continued until final proofs went to the printer. At that point, I could only pray that if I'd done my best, it would be enough.
All style elements of the book were decided in advance and coded into manuscript for a consistent format.
A critical decision was how much "white space" to include. White space is the blank area around figures and tables and separates paragraphs, bullet points, and numbered steps. It's a kind of visual punctuation that makes life easier for students. The fight for white space was real: I wanted more, the publisher wanted less. (They relented.)
I chose the book's color palette from paint chips, with the simple premise that beautiful colors would set the mood for beautiful physiology. Muted shades like Honest Blue, Lemon Butter, Mellow Mango, and Sumptuous Peach created the "welcome to physiology" feeling I hoped to convey.
The typeface had to be clean, open, and easy on the eyes. I asked students to test five finalists while riding the campus bus, in other words reading while moving. The winner, chosen from the classic Palatino family, has endured through eight editions. When an editor innocently proposed a new typeface, the decibels in my "Are you kidding?" probably scared her to death.
When the entire manuscript was complete, it went to production, where a compositor turned it into book pages. Six months later, I received the proofs to check for compositor's errors. It turns out that every special feature of physiology -- symbols, equations, calculations, notations like sub- and superscripts -- has the potential to be botched by the compositor. It was up to me to spot alphas that should have been betas, subscripts that should have been superscripts, misaligned table columns, figures placed three pages after their "call out" in text, non-sensical line breaks, and butchered equations. In the first edition's pulmonary chapter alone, I had to correct more than 75 significant compositor's errors.
I developed a system for finding errors in proofs by first checking all symbols and special terms in text, then equations and sample calculations, then bullets and numbered lists, then headings and paragraph breaks, then tables, then figure legends and figure placement. I wrote a detailed note about each error and typically ended the note with "see manuscript and previous edition." As the number of errors in a chapter grew, my patience wore thin. Initially, I blew off steam in the notes with, "Did you even look at the previous edition?" "Has anyone checked this before me?" "Did you fall asleep?" Then, I pictured an underpaid compositor who was only doing what they were told ("Hurry up, time's money") and softened my rhetoric.
The pressure to find typos never let up. A missed typo in this final stage would make it into the printed book; it would glare at me from the page and wag its fingers.
The first edition of the book was published on time and found its audience in the US and abroad. Almost immediately, the publisher proposed a second edition to be published four years later. An every-four-year-cycle for new editions has continued to this day, for almost 30 years.
As soon as a new edition is published, I start marking up my copy with detailed "notes to self." When it's time to begin work on the next edition, my copy has hundreds of colored flags noting changes to be made. Everything is up for grabs. If a section is in good shape, great. Otherwise, I'm looking to improve all text, figures, and tables. I expand the index in every edition, since an index can never be too complete.
Student feedback is crucial in the revision process. Students are the bottom line, and if something isn't working for them, I need to know. Over eight editions, I've received hundreds of notes. Some are heart-warming votes of confidence, "I love physiology now," (fire emoji) or "It feels like you know me," or "I sleep with Costanzo Physiology under my pillow." Others start endearingly with, "I'm not sure what my question is, but perhaps you can help." (I try.) Mostly, there are specific suggestions to improve explanations, fix details in the science, or expand coverage. Occasionally, readers will say the book is not for them.
Years ago, Mr. All Caps grabbed a megaphone and screamed that my book was a "waste of time."
I'd had negative feedback before, in course reviews, online forums, and reviews solicited by the publisher. But this felt different. His words stuck in my craw and wouldn't let go.
After years of brooding, I've come to a few conclusions about why I couldn't shake this episode and move on. For one, his words felt personal and gratuitous. I even had the sad thought that this student may have sat in my office. For another, his words were public, seen widely by students and colleagues whose opinions I cared about. His words felt haughty and authoritative. The icing on the cake, of course was the all-caps; lower case was not sufficient to express his disdain. These things partly explain why I was so bothered.
However, I believe the most important reason for my outsized reaction is this: for me, nothing could be worse than a student saying that I wasted their time. In all that I do, whether teaching, advising, writing books, even simple emails, I try to respect my students' time. Time, that precious, irreplaceable resource. Protecting others' time is a personal ethos. To have said that my work "wasted his time" was the profoundest insult I could have received.
This essay is one kind of defense. It explains how I created a book to the best of my ability -- a book fashioned in the manner of TSIOC -- a book meant to be useful to any student, whether a physiology-lover or a physiology-skeptic. A book meant to be highlighted, dogeared, and held close.
But plumbing the depths of the hurt I felt when my student proclaimed I'd wasted his time -- that may take the rest of my life.
References
1. Costanzo LS.Physiology. Philadelphia, PA: W.B. Saunders, 1998.
2. Costanzo LS.Costanzo Physiology. 8th ed. Philadelphia, PA: Elsevier, 2027.
3. Shriner RL, Fuson RC, Curtin DY.The Systematic Identification of Organic Compounds. 5th ed. New York, NY: John Wiley & Sons, 1964.
[1] The equation that predicts turbulence is the Reynolds number (NR) : NR = rdv/h, where r is density of blood, d is diameter of the blood vessel, v is velocity of blood flow, and h is viscosity of blood. The higher the Reynolds number, the greater the likelihood of turbulent blood flow. According to the equation, narrowing of a blood vessel (decreasing diameter in the numerator) should decrease the Reynolds number and decrease turbulence. Therein the puzzle, since narrowing of blood vessels causes the opposite, increased turbulence and murmurs. What's going on? The equation can't be wrong, but neither can murmurs be wrong. The puzzle is explained by a twist in the math. Velocity of blood flow is also in the numerator of the Reynolds number equation, where velocity of blood flow = blood flow/area and area = p r2. Thus, velocity increases as radius (or diameter) decreases, raised to the second power; the dependence of Reynolds number on velocity is more powerful than the dependence on diameter. Puzzle solved!