One Hundred Books About Physics for Medicine and Biology

When I was in high school, I became intrigued by St. John’s College and their Great Books program. I had their brochure, which included a list of the books to read each year; the most famous works of western civilization.

In the spirit of St. John’s, below I list one hundred Great Books about physics applied to medicine and biology. Read all these and you will have obtained a liberal education in biological and medical physics. One book you won’t find on this list is Intermediate Physics for Medicine and Biology. I’m going to assume you’ve already read IPMB and my goal is to suggest books to supplement it.

Where to begin? I’ll assume you have taken a year of physics and a year of calculus. Once you have these prerequisites, start reading.

1. Powers of Ten. First an overview that’s easy and fun. It provides an intuitive feel for the relative sizes of things. 
2. The Machinery of Life. Although I’m assuming you’ve studied some physics and math, I’m not assuming you have much background in biology. This book provides a gentle introduction to biochemistry. Plus, it has those wonderful drawings by David Goodsell. 
3. The Art of Insight in Science and Engineering. Remember: We seek insight, not just facts.
4. Physical Models of Living Systems. IPMB is about modeling in medicine and biology. Philip Nelson’s little book gets us started building models. 
5. The Feynman Lectures on Physics. I know, I know...you’ve already studied introductory physics, but The Feynman Lectures are special. You don’t want to miss them, and they contain some biology too.
6. Air and Water. Now we get to our main topic: physics applied to biology. Mark Denny’s book covers many topics found in the first half of IPMB.
7. Physics with Illustrative Examples from Medicine and Biology. This classic three-volume set covers much of the same ground as IPMB.
8. The Double Helix. To further strengthen your background in biology, read James Watson’s first-person account of how he and Francis Crick discovered the structure of DNA. It’s a required text for any student of science, and is an easy read.
9. The Eighth Day of Creation: The Makers of the Revolution in Biology. After warming up with The Double Helix, it’s time to dig deeper into the history and ideas of modern biology. Physicists play a large role in this book, and it’s wonderfully written.
10. Biomechanics of Human Motion. Chapter 1 in IPMB covers statics applied to the bones and muscles of the body. It’s our first book that focuses in detail on a specific topic.
11. Structures, or Why Things Don’t Fall Down. A delightful book about mechanics, including some biomechanical examples. It’s one of the most enjoyable books on this list. Don’t miss the sequel, The New Science of Strong Materials.
12. Biomechanics: Mechanical Properties of Living Tissue. We need a book about biomechanics that treats tissue as a continuous medium. YC Fung’s textbook fills that niche.
13. A Treatise on the Mathematical Theory of Elasticity. This book is long and technical, and may contain more material than you really need to know. Nevertheless, it’s a great place to learn elasticity. I’m sure there are more modern books that you may prefer. Skip if you’re in a hurry.
14. The Physics of Scuba Diving. An easy read about how hydrostatics impacts divers.
15. Life in Moving Fluids. Fluid dynamics is one of those topics that’s critical to life, but is often skipped in introductory physics classes. This book by Steven Vogel provides an excellent introduction to the field of biological fluid dynamics.
16. Vital Circuits. Another book by Vogel, which focuses on the fluid dynamics of the circulatory system. 
17. Boundary Layer Theory. This large tome may be too advanced for the list, but I learned a lot from it. Skip if you need to move along quickly.
18. Textbook of Medical Physiology. We need to get serious about learning physiology. This classic text is by Arthur Guyton, but any good physiology textbook will do. Not much physics here. The book contains more biology than we need, but physiology is too important to skip.
19. e, The Story of a Number. A gentle introduction into calculus and differential equations, and a great history of the exponential function, the topic of IPMB’s second chapter.
20. Quick Calculus. Yes, you already studied calculus. But we are about to get more mathematical, and this book will help you brush up on math you may have forgotten. If you don’t need it, move on. 
21. Used Math. Finish your math review with this outline of mathematics essential for college physics.
22. The Essential Exponential. It’s time to focus specifically on the exponential function and its properties, so important in biology and medicine.
23. A Change of Heart. Chapter 2 of IPMB mentions the Framingham heart study. Read the story behind the project.
24. On Being the Right Size. This is really an essay, but indulge me while I include it here among the books. J. B. S. Haldane is too fascinating of a writer to miss.
25. Scaling: Why is Animal Size so Important? Knut Schmidt-Nielsen’s study of scaling, a key topic in Chapter 2 of IPMB.
26. Lady Luck. Chapter 3 of IPMB requires us to know some probability, and Warren Weaver’s book is an engaging introduction.
27. Statistical Physics. The first few sections of Chapter 3 in IPMB develop the ideas of statistical physics in a way reminiscent of Frederick Reif’s volume in the Berkeley Physics Course.
28. An Introduction to Thermal Physics. For those who want a more traditional approach to thermodynamics, I recommend Daniel Schroeder’s textbook.
29. Lehninger Principles of Biochemistry. Biological thermodynamics overlaps with biochemistry. Any good biochemistry book will do. They all contain more detail than you need, but a biological physicist must know some biochemistry.
30. The Second Law. This delightful book by Peter Atkins will fill a hole in IPMB: a penetrating discussion about the second law of thermodynamics.
31. Div Grad Curl and All That. Chapter 4 of IPMB uses vector calculus, and there is no better introduction to the topic.
32. Random Walks in Biology. Howard Berg’s wonderful little book about diffusion.
33. The Mathematics of Diffusion. John Crank’s intimidating giant tome about diffusion. Mathephobes shouldn’t bother with it; Mathephiles shouldn’t miss it.
34. Conduction of Heat in Solids. Like the book by Crank, this ponderous textbook by Horatio Carslaw and John Jaeger presents all you ever want to know about solving the heat equation (also known as the diffusion equation).
35. How Animals Work. Another delightful book by Schmidt-Nielsen that considers comparative physiology, and topics in Chapter 5 of IPMB such as countercurrent heat exchange.
36. The Nuts and Bolts of Life. A colorful book about the first dialysis machine.
37. The Biomedical Engineering Handbook. Don’t read this encyclopedia-like multi-volume handbook in one sitting. Yet it provides dozens of examples of how physics is applied to medicine. Ask your library to buy this set and the next one.
38. Encyclopedia of Medical Devices and Instrumentation. The title should be Case Studies: How Physics is Applied to Medicine.
39. Plant Physics. IPMB doesn’t say much about plants, but physics impacts botany as well as zoology.
40. Nerve, Muscle, and Synapse. Bernard Katz’s excellent, if somewhat dated, introduction to all the electrophysiology you need for Chapter 6 of IPMB.
41. The Conduction of the Nervous Impulse. Read about the Hodgkin-Huxley model from the pen of Alan Hodgkin himself.
42. From Neuron to Brain. A modern introduction to neuroscience.
43. Electricity and Magnetism. This book by Ed Purcell is part of the Berkeley Physics Course. The first of three physics books about electricity and magnetism.
44. Introduction to Electrodyamics. David Griffiths’s text competes with Purcell’s for my favorite electricity and magnetism book.
45. Classical Electrodynamics. John David Jackson’s famous graduate-level physics text may be more electricity and magnetism than you want, but how could I leave it off the list?
46. Galvani’s Spark. A history of neurophysiology.
47. Shattered Nerves. A fascinating look at using electrical stimulation to compensate for neural injury. A history of neural prostheses.
48. Bioelectricity: A Quantitative Approach. The first, and probably easiest, of three bioelectricity textbooks.
49. Bioelectromagnetism. Jaakko Malmivuo and Robert Plonsey’s big book about bioelectricity.
50. Bioelectricity and Biomagnetism. Another big tome. Ramesh Gulrajani’s alternative to Malmivuo and Plonsey.
51. The Art of Electronics. In order to understand voltage clamping and other electrophysiological methods, you need to know some electronics. This book is my favorite introduction to the topic. 
52. Mathematical Handbook of Formulas and Tables. Chapter 6 contains lots of mathematics, and the next three books are references you may want. This Schaum’s Outline contains most of the math you’ll ever need. It’s cheap, light, and easy to use. Keep it handy.
53. Handbook of Mathematical Functions with Formulas, Graphs and Mathematical Tables. No one would sit down and read this handbook straight through, but “Abramowitz and Stegun” is invaluable as a reference.
54. Table of Integrals, Series, and Products. “Gradshteyn and Ryzhik” is the best integral table ever. Let the library buy it, but have them keep it in the reference section so you can find it quickly. 
55. Numerical Recipes. If you want to solve the equations of the Hodgkin-Huxley model, you need to program a computer. This book is great for finding the needed numerical methods.
56. Numerical Methods that Work. Forman Acton’s book is more chatty than Numerical Recipes, but full of insight.
57. Machines in our Hearts. Chapter 7 of IPMB examines the heart. Read this history of pacemakers and defibrillators to put it all in perspective.
58. Cardiac Electrophysiology: From Cell to Bedside. This multi-author, multi-edition work contains everything you always wanted to know about the electrical properties of the heart, but were afraid to ask.
59. Cardiac Bioelectric Therapy. Another multi-author collection, with several excellent chapters about the bidomain model.
60. When Time Breaks Down. Art Winfree’s unique analysis of the electrical properties of the heart.
61. Electric Fields of the Brain. Paul Nunez’s book about the electroencephalogram from the perspective of a physicist.
62. Iron, Nature’s Universal Element. Why people need iron and animals make magnets.
63. The Spark of Life. An accessible introduction to electrophysiology and ion channel diseases.
64. Ion Channels of Excitable Membranes. The definitive textbook about ion channels, by Bertil Hille.
65. Voodoo Science. Some of the topics in Section 9.10 of IPMB about possible effects of weak electric and magnetic fields make me yearn for this hard-hitting book by Bob Park.
66. Dynamics: The Geometry of Behavior. Chapter 10 of IPMB covers nonlinear dynamics. This beautiful book introduces dynamics using pictures.
67. From Clocks to Chaos. Leon Glass and Michael Mackey introduce the idea of a dynamical disease.
68. Nonlinear Dynamics and Chaos. Steven Strogatz’s classic; my favorite book about nonlinear dynamics.
69. Mathematical Physiology. An award-winning textbook about applying math to biology.
70. Mathematical Biology. Another big fine textbook for the mathematically inclined.
71. The Geometry of Biological Time. A quirky book by Art Winfree, more wide-ranging than When Time Breaks Down.
72. Data Reduction and Error Analysis for the Physical Sciences. Many of the ideas about least squares fitting discussed in Chapter 11 of IPMB are related to analyzing noisy data.
73. The Fourier Transform and its Applications. The Fourier transform is the most important concept in Chapter 11. Ronald Bracewell’s book is a great place to learn about it.
74. Introduction to Membrane Noise. Louis DeFelice’s book explains how to deal with noise.
75. Naked to the Bone. A historical survey of medical imaging.
76. Medical Imaging Physics. A book by William Hendee and E Russell Ritenour, at a level similar to IPMB but dedicated entirely to imaging. Also see its partner, Hendee's Radiation Therapy Physics.
77. Foundations of Medical Imaging. A big, technical book about imaging.
78. Theoretical Acoustics. Not much biology here, but a definitive survey of acoustics to back up Chapter 13 of IPMB.
79. Physics of the Body. This book discusses many topics, including hearing.
80. Musicophilia. An extraordinary book by Oliver Sacks about the neuroscience of hearing.
81. Quantum Physics of Atoms, Molecules, Solids, Nuclei, and Particles. My choice for a modern physics textbook, with much information about the interaction of light with matter.
82. The First Steps in Seeing. Robert Rodieck’s incredible book about the physics of vision.
83. The Optics of Life. This masterpiece by Sonke Johnsen walks you through optics, examining all the biological applications. A great supplement to Chapter 14 of IPMB.
84. From Photon to Neuron. A study of light, imaging, and vision.
85. Introduction to Physics in Modern Medicine. Suzanne Amador Kane’s nice introduction to physics applied to medicine, covering many topics in the last half of IPMB.
86. Introduction to Radiological Physics and Radiation Dosimetry. Frank Herbert Attix wrote the definitive textbook about how x-rays interact with tissue, a topic covered in Chapter 15 of IPMB.
87. Radiobiology for the Radiologist. The go-to reference for how cells and tissues respond to radiation.
88. Molecular Biology of the Cell. The classic textbook of cell biology.
89. Radiation Oncology: A Physicists Eye View. Explains how to treat cancer using radiation.
90. The Physics of Radiation Therapy. Faiz Khan’s in-depth study of radiation therapy.
91. The Atomic Nucleus. An classic about nuclear physics, providing background for Chapter 17 of IPMB. You could replace it with one of many modern nuclear physics textbooks.
92. The Immortal Life of Henrietta Lacks. A fascinating study of how a women treated for cancer using radioactivity ended up providing science with an immortal cell line.
93. Strange Glow. How radiation impacts society.
94. The Radium Girls. This book is about women poisoned by radium-containing paint (lip, dip, paint). It reminds us why we study medical physics.
95. Magnetic Resonance Imaging: Physical Properties and Sequence Design. All you need to know about MRI.
96. Principles of Nuclear Magnetic Resonance Microscopy. Paul Callaghan’s view of magnetic resonance imaging.
97. Echo Planar Imaging. Advanced MRI techniques.
98. Biological Physics. IPMB is not strong in covering physics applied to cellular and molecular biology. Here are three great books to fill that gap.
99. Cell Biology by the Numbers. I love the quantitative approach to biology.
100. Physical Biology of the Cell. How physicists view biology. 

Don’t see your favorite listed? Here’s my call to action: Add your recommendations to the comments below.

I didn’t end up going to St. John’s College and studying the Great Books. Instead, I attended a more traditional school, the University of Kansas. I loved KU, and I have no regrets. But sometimes I wonder...

Suki Roth (2002-2018)

Suki Roth (2002-2018).

Regular readers of this blog are familiar with my dog Suki, who I’ve mentioned in more than a dozen posts. Suki passed away this week. She was a wonderful dog and I miss her dearly.

Suki and I used to take long walks when I would listen to audio books, such as The Immortal Life of Henrietta Lacks, Musicophilia, Destiny of the Republic, Galileo’s Daughter, and First American: The Life and Times of Benjamin Franklin. This list just scratches the surface. On my Goodreads account, I have a category called “listened-to-while-dog-walking” that includes 84 books, all of which Suki and I enjoyed together. 

In my post about the Physics of Phoxhounds, I mentioned that a photo of Suki and me (right) was included in Barb Oakley’s book A Mind for Numbers: How to Excel at Math and Science (Even if You Flunked Algebra). Recently I learned that Barb’s book has sold over 250,000 copies, making Suki something of a celebrity.

Suki helped me explain concepts from Intermediate Physics for Medicine and Biology, such as age-related hearing loss and the biomechanics of fleas. Few people knew that she had this secret career in biomedical education!

Thanks to Dr. Kelly Totin, and before her Dr. Ann Callahan, and all the folks at Rochester Veterinary Hospital for taking such good care of Suki. In particular I appreciate Dr. Totin’s help during Suki’s last, difficult days. As she said near the end, her focus was on the quality of Suki’s time left rather than the quantity; an important life lesson for us all.

I’ll close with a quote from one of my favorite authors, James Herriot. In his story “The Card Over The Bed,” the dying Miss Stubbs asks Herriot, a Yorkshire vet, if she will see her pets in heaven. She was worried because she had heard claims that animals have no soul. Herriot responded “If having a soul means being able to feel love and loyalty and gratitude, then animals are better off than a lot of humans. You’ve nothing to worry about there.”

Suki resting.

Suki with her nephew Auggie.

Suki with all five editions of IPMB.

Suki (right), her niece Smokie (the Greyhound, center),
and her nephew Auggie (the Foxhound, left),
about to get treats from my wife Shirley.

Suki and me, 15 years ago.

Young Suki

Principles of Musical Acoustics

Principles of Musical Acoustics,
by William Hartmann.

In the 4th edition of Intermediate Physics for Medicine and Biology, Russ Hobbie and I added a new chapter (Chapter 13) about Sound and Ultrasound. This allows us to discuss acoustics and hearing; an interesting mix of physics and physiology. But one aspect of sound we don’t analyze is music. Yet, there is much physics in music. In a previous blog post, I talked about Oliver Sacks’ book Musicophilia, a fascinating story about the neurophysiology of music. Unfortunately, there wasn’t a lot of physics in that work.

Last year, William Hartmann of Michigan State University (where my daughter Kathy is now a graduate student) published a book that provides the missing physics: Principles of Musical Acoustics. The Preface begins

Musical acoustics is a scientific discipline that attempts to put the entire range of human musical activity under the microscope of science. Because science seeks understanding, the goal of musical acoustics is nothing less than to understand how music “works,” physically and psychologically. Accordingly, musical acoustics is multidisciplinary. At a minimum it requires input from physics, physiology, psychology, and several engineering technologies involved in the creation and reproduction of musical sound.

My favorite chapters in Hartmann’s book are Chapter 13 on Pitch, and Chapter 14 on Localization of Sound. Chapter 13 begins

Pitch is the psychological sensation of the highness or the lowness of a tone. Pitch is the basis of melody in music and of emotion in speech. Without pitch, music would consist only of rhythm and loudness. Without pitch, speech would be monotonic—robotic. As human beings, we have astonishingly keen perception of pitch. The principal physical correlate of the psychological sensation of pitch is the physical property of frequency, and our keen perception of pitch allows us to make fine discriminations along a frequency scale. Between 100 and 10,000 Hz we can discriminate more than 2,000 different frequencies!

That is two thousand different pitches within a factor of one hundred in the range of frequencies (over six octaves), meaning we can perceive pitches that differ in frequency by about 0.23 %.  A semitone in music (for example, the difference between a C and a C-sharp) is about 5.9 %. That's pretty good: twenty-five pitches within one semitone. No wonder we have to hire piano tuners.

Pitch is perceived by “place,” different locations in the cochlea (part of the inner ear) respond to different frequencies, and by “timing,” neurons spike in synchrony with the frequency of the sound. For complex sounds, there is also a “template” theory, in which we learn to associate a collection of frequencies with a particular pitch. The perception of pitch is not a simple process.

There are some interesting differences between pitch perception in hearing and color perception in vision. For instance, on a piano play a middle C (262 Hz) and the next E (330 Hz) a factor of 1.25 higher in frequency. What you hear is not a pure tone, but a mixture of frequencies—a chord (albeit a simple one). But if you mix red light (450 THz) and green light (563 THz, again a factor of 1.25 higher in frequency), what you see is yellow, indistinguishable by eye from a single frequency of about 520 THz. I find it interesting and odd that the eye and ear differ so much in their ability to perceive mixtures of frequencies. I suspect it has something to do with the eye needing to be able to form an image, so it does not have the luxury of allocating different locations on the retina to different frequencies. One the other hand, the cochlea does not form images, so it can distribute the frequency response over space to improve pitch discrimination. I suppose if we wanted to form detailed acoustic images with our ear, we would have to give up music.

Hartmann continues, emphasizing that pitch perception is not just physics.

Attempts to build a purely mechanistic theory for pitch perception, like the place theory or the timing theory, frequently encounter problems that point up the advantages of less mechanistic theories, like the template theory. Often, pitch seems to depend on the listener’s interpretation.

Both Sacks and Hartmann discuss the phenomena of absolute, or perfect, pitch (AP). Hartmann offers this observation, which I find amazing, suggesting that we should be training our first graders in pitch recognition.

Less than 1% of the population has AP, and it does not seem possible for adults to learn AP. By contrast, most people with musical skills have RP [relative pitch], and RP can be learned at any time in life. AP is qualitatively different from RP. Because AP tends to run in families, especially musical families, it used to be thought that AP is an inherited characteristic. Most of the modern research, however, indicates that AP is an acquired characteristic, but that it can only be acquired during a brief critical interval in one’s life—a phenomenon known as “imprinting.” Ages 5–6 seem to be the most important.

My sister (who has perfect pitch) and I both started piano lessons in early grade school. I guess she took those lessons more seriously than I did.

In Chapter 14 Hartmann addresses another issue: localization of sound. It is complex, and depends on differences in timing and loudness between the two ears.

The ability to localize the source of a sound is important to the survival of human beings and other animals. Although we regard sound localization as a common, natural ability, it is actually rather complicated. It involves a number of different physical, psychological, and physiological, processes. The processes are different depending on where the sound happens to be with respect to the your head. We begin with sound localization in the horizontal plane.”

Interestingly, localization of sound gets more difficult when echos are present, which has implications for the design of concert halls. He writes

A potential problem occurs when sounds are heard in a room, where the walls and other surfaces in the room lead to reflections. Because each reflection from a surface acts like a new source of sound, the problem of locating a sound in a room has been compared to finding a candle in a dark room where all the walls are entirely covered with mirrors. Sounds come in from all directions and it’s not immediately evident which direction is the direction of the original source.

The way that the human brain copes with the problem of reflections is to perform a localization calculation that gives different weight to localization cues that arrive at different times. Great weight is placed on the information in the onset of the sound. This information arrives directly from the source before the reflections have a chance to get to the listener. The direct sound leads to localization cues such as ILD [interaural level difference], ITD [interaural time difference], and spectral cues that accurately indicate the source position. The brain gives much less weight to the localization cues that arrive later. It has learned that they give unreliable information about the source location. This weighting of localization cues, in favor of the earliest cues, is called the precedence effect.

The enjoyment of music is a truly complicated event, involving much physics and physiology. The Principles of Musical Acoustics is a great place to start learning about it.

Musicophilia

Musicophilia: Tales of
Music and the Brain,
by Oliver Sacks.

Those who know me well are aware that I spend considerable time walking my dog Suki. Usually during these walks I am listening to recorded books. Being too cheap to spend money on this habit, I borrow these recordings from the Rochester Hills Public Library. They have a impressive selection, but Suki and I have been at this for a while (she is almost 11 years old), and I have slowly worked my way through their stock of recordings in genres that I ordinarily listen to; science, history, and biography. I don’t view this as a problem, because it has forced me to sample books about topics I would not ordinarily listen to. The most recent example is Musicophilia: Tales of Music and the Brain, by Oliver Sacks. Perhaps you object that this is a science book, but I view it more as a medical book outside my normal experience. Regardless, I was pleasantly surprised to find considerable medical physics discussed.

I had listened previously to Sacks’s delightfully-titled The Man Who Mistook His Wife for a Hat, so I knew what I was getting into. In Musicophilia, Sacks discusses a variety of abnormalities in the perception of music. For instance, he begins with musical hallucinations. This is more than just having a song stuck in your head. These were examples from his clinical practice of people who had, say, suffered a brain injury and afterward would hear music in their mind that they could not distinguish from real music. They sometimes could not turn it on or off, but were stuck with it more or less continuously. Another example is people who, after a stroke, lost the ability to hear music as music. An opera sounds like someone screaming, and a symphony like pots and pans crashing onto the floor. In one case he related, this occurred to a former professional musician. It’s amazing.

Sacks describes all sorts of brain studies being done to examine these patients. There is considerable discussion of data measured using electroencephalography, magnetoencephalography, positron emission tomography, functional magnetic resonance imaging, and transcranial magnetic stimulation—all of which Russ Hobbie and I analyze in the 4th edition of Intermediate Physics for Medicine and Biology. For me, hearing these stories makes me nostalgic for my years working at the National Institutes of Health, where I used to collaborate with neurologists such as Mark Hallett (whose research is mentioned by Sacks). Hallett and his team studied all sorts of odd diseases while I was helping them develop magnetic stimulation. In this case, we physicists and engineers were not discovering new biological ideas or medical abnormalities, but we were providing the tools for others to make these discoveries. And, oh, what tools!

Sacks notes there are some patients who have lost their ability to tell which of two tones is the higher pitch (but can still hum a song). These patients are in contrast with those rare individuals with perfect or absolute pitch; they can tell what note a sound is when heard in isolation. My sister has something approaching perfect pitch. When I was in high school, I took piano lessons. Whenever I played a wrong note while practicing (which was quite often) she would call out from an adjacent room “F-sharp!” or “B-flat!” Do you know how annoying it is not only to have your mistakes pointed out for all to hear, but also to have the specific note identified precisely? Worst of all, she was always right. Some of these piano pieces she had played herself, but others she had not; she was just able to identify the pitch. I have always envied people with perfect pitch, but Sacks raises an interesting point. If people with perfect pitch hear a song played flawlessly but in the wrong key, they get all agitated and upset (he compared this to seeing a painting with all the colors wrong). I, on the other hand, would remain blissfully unaware of the problem. When I was in graduate school in Nashville, I bought a used piano from a blind fellow who refurbished pianos for a living. This particular piano was so old that he could not tighten its strings completely, so the piano was tuned about 3 steps too low (He gave me a good deal on it). The improper tuning never bothered me in the least (my sister hated that piano). However, sometimes my weakness with tonal discrimination has caused me some embarrassment. I played tuba in my high school band, and before concerts the director would have us all “tune up”. The first clarinet would play a note, and we would each play the same note in turn to make sure we were in tune. I always hated this, because I could never tell if I was sharp or flat, and the director would usually end up yelling at me in frustration “You’re flat. Flat! Push the tuning slide in!”

Sacks’s book got me to thinking about all sorts of unusual sensory perceptions. He describes people who could hear but could not perceive music, and I thought it must be like someone born without sight. But Sacks had a better analogy; imagine someone born colorblind (say, completely color blind, instead of just lacking one of three color receptors). How do you describe color to such a person? It has no meaning. How do you describe music to someone born unable to make sense of it? Then I began thinking of other odd sensory inputs, like magnetoreception and the ability to perceive the polarization of light. Humans can’t perceive these signals, but other species can. If you will let me indulge in a bit of anthropomorphization, I suspect there are some bird families who sit in their nest at night saying to each other “those humans can’t perceive magnetic fields or polarization! How to they ever get home?”

Finally, for those of you who know Suki, let me provide a quick update. Earlier this year she damaged her anterior cruciate ligament, and our walks came to an abrupt halt. After much debate (she is a small dog, and is 10 years old) we decided to have her undergo surgery. The veterinary surgeon Dr. McAbee did a marvelous job, and we are now back to our walks as if nothing ever happened.