I want to cast doubt on something I read some time ago in a textbook of physiology originally written for nurses. But it relates to faeces and its smell and the more I look into the spelling of poo and/or pooh the more confused it gets. Both spellings can be used as nouns and as verbs. Both have the same dictionary definitions. I was expecting ‘poo’ to relate to a piece of faeces and ‘pooh’ to an unpleasant smell - not least, the smell of poo! This careful placing of the ‘h’ would have been important, I assumed. In that way, one could talk about the pooh (smell) of poo (faeces). But things are not so simple.
Referring back to that textbook of physiology originally written for nurses - which I shall, of course, refrain from naming. When it came to reading about the liver and bile, I came across something that, at the time I merely accepted but now, much later on doubt very much.
Bile is a secretion from the liver that enters the duodenum via a system of bile ducts. Often people assume that bile is primarily a waste product since it gets mixed with the gut contents which, of course, go on to form the faeces. Although there are some waste products to be found in the bile, this assumption is incorrect. Indeed, a significant proportion of the bile is reabsorbed. The bile has a beneficial role in the digestive process. It acts as an emulsifier aiding fat absorption, and is important for the absorption of the fat soluble vitamins A, D, E, and K. It neutralises the acidity of the stomach contents as they are released into the duodenum, and it also acts as a bactericide.
What that old textbook also claimed was that it deodorised the faeces. I am not disputing whether it may have that effect. What I want to question is any suggestion that this is in any way purposive. Unfortunately, that was the suggestion that textbook gave.
That there should be a mechanism for making the human faeces less smelly seems odd. Interestingly, nobody finds the smell of their own faeces completely intolerable. But when it comes to the smell of other people’s that is a different matter. All faeces, even one’s own, are to be avoided and any signal - including olfactory - that aids in that avoidance has a survival advantage. That we find faeces repugnant has a biological basis. The bactericidal effect of bile is clearly in keeping with this whereas deliberate deodorisation is not. Indeed, it potentially runs contrary to this. Furthermore, as a species, we do not have a particularly highly developed sense of smell anyway. Surely, it would be to our species’ advantage to make our faeces more smelly not less so.
This is another warning about taking what we read simply at face-value. Students often assume that textbooks are definitive, having the last word on its subject matter. I once had a student who was very reluctant to question any textbook. She even described their contents as ‘written in stone.’ It was hard to convince her otherwise.
Another student, years latter, spent some time in the USA as a postdoctoral student in a prestigious academic department. At that time, an eminent colleague was preparing a new edition of one of the world’s most authoritative biology textbooks. Readers naturally assume that person to have written the book. But that is not the case. Instead, graduate students were pressed into writing different sections which were then stitched together. What the student used to do was to simply crib from other textbooks! So one of the world’s most authoritative biological textbooks is really a composite of other less well respected tomes - paraphrased.
