♫♫♫ ..."and the sign said "Long-haired freaky-looking people need not apply..." ♫-♫-from the song "Signs" by The Five Man Electrical Band (1971; redone later by Tesla)Sorry, I didn't mean that kind of Hair.More like this kind:This book deals with the diagnosis and classification of diseases which affect hair follicles. It is filled with beautiful color plates illustrating the histopathological features of different hair-related conditions on microscopic sections. I would characterize the images here as better-than-average quality, as pathology textbooks go. For one thing, all the images are all in color, which is nice, since obviously the microscopic images a pathologist deals with in daily practice are in color. The author has a very laid back style, and a very broad-scope gestalt way of explaining things, which makes the text enjoyable to read. If the book has any shortcomings, I'd say that despite the title, there isn't that much clinical correlation; not as much as you would find in something like Weedon's Skin Pathology, or Leaver's Histopathology of the Skin. Overall, however, I found it to be quite helpful for clinical use in a hospital-based general pathology practice. In a setting like that, the general surgical pathologist, or even dermatopathologist, probably just needs the reference book to confirm a general impression of what the pathologic process is, and whether referral to an expert is needed. More difficult cases will almost always go to a consultant who specializes in hair pathology. "Hair pathology." That sounds a bit funny, doesn't it? This is one of those super sub-specialty areas that most people never think about, unless it directly affects them. Hair follicles are one of the "adnexal" structures of the skin, which of plays a role in the body's heat regulation. The book focuses on histopathologic diagnosis, but beyond that, I've got my own musings on the subject, which I will now subject you to, should you choose to read further.Hair and hair styling is diverse across different cultures, because it is an aspect of one's personal appearance which lends itself to a stylization; there is just a wide variation in how we can choose to manipulate it. Most people can't do much about the bone structure of their face, or the color of their skin, but there's a LOT of different things they can do with their hair, in the way of personal expression. I guess I'm not saying anything you don't know already, but this discussion is an excuse to post some of the more extreme crazy hairstyles I found on the internet.Heh, freaks. Here's one for chest hair.That one's kind of cool, though.Speaking of the cultural importance of hair: let's not forget about military recruits. When they are inducted into service, their hair is cut short. This is done partly to reduce differences in physical appearance between members of a unit, encouraging group cohesion, and identification of their fellow recruits as fellow cogs in a larger functioning unit. It is also done to differentiate military members from civilians, for the purposes of morale, group cohesion, and esprit de corps. It is also done to drive home to each recruit how he is no longer in charge of his own life... down to the very personal matters of how he chooses to present himself through grooming to the outside world. The same is done with clothing, in the form of a military uniform. So yes, hair has a lot of important cultural significance.Let's go back to medicine for a second. The subject of hair seems to bridge the gap between our biology and our group behavior. One's hair condition can be an indicator of health, because hair quality is easily compromised by poor nutrition and a wide range of diseases, including immune dysregulation, hormonal status (e.g. the premature appearance of pubic hair in prepubescent kids can be an indication of pituitary or adrenal tumor), toxicity of foreign substances (e.g. Thallium toxicity causes hair loss, as well as some chemotherapeutic agents), even psychiatric conditions. A lot of things need to be going right, in order to have nice hair. Judges at dog shows know this, but the same goes for humans. You don't get a beautiful coat like this without being healthy!The third year of medical school is the time when students work on their observational skills, developing their abilities to examine patients. I remember being evaluated on my patient exam skills. I remember one of the things a lot of students lost point on was failing to observe the patient's hair for clues about their diagnosis.Here are a few examples of hair reflecting disease states:Pellagra (niacin deficiency) is remembered by medical students with the mnemonic "dermatitis, dementia, diarrhea and death". Patients lose color in their hair, and eventually lose their hair. Here's patchy loss of male facial hair due to alopecia aerata.Here's hairloss due to a psychiatric condition called Trichotillomania (pathologically hair pulling):Here's an example of hair loss in a fourteen year old with Thallium toxicity.The book covers a wide range of other conditions too. ...So accepting that hair can be an indicator of health, let's reconsider the significance of hairstyles. One of the favorite studies in anthropology is the matter of how mates are selected. Hair as an indicator of health becomes hair as an indicator of fitness to bear children, when selecting mates. Thus, healthy, stylish hair is necessarily tied in with our perception of mate fitness and thus with our ideas of beauty. Look at what our popular culture considers beautiful: young reproductive-age women with big breasts and long, luxurious, healthy hair signaling their fitness and fertility.The attraction of these features is pretty universally hardwired into the male brain. What's interesting, at least in the West, is how many women, once they pass some (unspecified) age, tend to all cut their hair short. You hardly ever see a woman in the West with long hair past 70 years old. It makes sense, in the context of what I'm saying; long hair is a lot of work, and if they have no cultural or biologic drive to signal fertility to potential mates, the long hair isn't "worth it". What's really funny in this discussion is when you look at younger women who choose to cut their hair short (probably because short hair is less work, or maybe because it is more suited to their job or daily activities). If they want to cut their hair short, that's fine, but the fact remains that most guys prefer the longer hair so often when a woman with newly-cut hair asks her mate what he thinks of her new 'do, she'll get some sort of searching, polite, noncomittal response like "Well, yes, it looks very practical." or something like that. Funnier still is when you watch how other women react when a woman cuts her hair. They gush all over it, inevitably exclaiming "How cute!!!", or something like that. Women seem to be far more enthusiastic than men about short hair on another woman. Perhaps their brains aren't hardwired with as strong a long hair preference as men, so maybe they really do like their friend's short hair. Some alternative explanations occur to me though, and I wonder if perhaps these might be the real reason they are so supportive of their friend's haircut. Perhaps their raving about "cute" short hair is really just an effort to increase the popularity of short hair... so that perhaps one day they might don a short style (which requires less effort to maintain) without sacrificing any of the fertility/beauty which long hair signals. More cynically, perhaps women encouraging short hairstyles in other women is really just a subconscious strategy to entice them into grooming themselves in a way that makes them less competitive for potential mates. God it sounds sexist when I say it like that. I don't mean it like that, honest, and I apologize to any short-haired women who may be offended. But you know what? I think these factors do exist, and have been bred into us over millions of years of evolution, and Biology doesn't give a damn if it sounds sexist. BLAME EVOLUTION!!