Flatus

This topic crosses certain boundaries. It is a topic of physiological interest but not one discussed in polite company. As such, it serves as a lesson in not allowing politeness to encumber academic investigation.

That the bowel produces gas is well known to everybody. Nobody alive has even not produced bowel gas. In the healthy individual, this gas is a natural byproduct of the activity of the symbiotic bacteria living in our large intestines. When teaching the large intestine, the production of this gas may be commented upon (in passing, pun intended), but this is not always the case. That this gas is often wilfully vented inevitably goes unremarked. This is despite the interesting fact that even when suffering from diarrhoea, we are often able to vent gas (albeit carefully) while successfully containing the liquid faeces. This suggests that the anal sphincter possesses a certain dexterity—for want of a better word. It is a pity that this dexterity is not more widely appreciated and discussed in lectures.

I remember a rather uncouth boy at school who deliberately broke wind in class one day and remarked to those sitting around him how nice he found its smell and how nice they ought to find it too! They did not; quite the opposite, of course. This does raise the question of why he liked it and the others did not.

I do not know why, but I do think it to be a reasonable question to pose. That we find some of the smells produced by others unpleasant may have something to do with the 'Yuk factor' or, to put it more scientifically, 'the wisdom of repugnance'. This is the notion that certain things that we find inherently unpleasant are also potentially harmful to us. In turn, the reaction to the unpleasantness prevents us from incurring any harm. Avoiding contact with faeces is obviously to our benefit. This may perhaps extend to the smells associated with them. Their smells may alert us to potential harm.

At the same time, being able to smell one’s own bowel gas when passed does provide us with a feedback mechanism of sorts. It does allow aspects of the chemistry of the bowel to be scrutinised consciously and, perhaps more importantly, subconsciously. Does bowel chemistry in terms of the gas smelt influence subsequent dietary choice?

That bowel gas has an odour, and the differing reactions to that odour are something socially unconscionable even in the lecture theatre. It is my contention that there are no barriers to what is allowed in the lecture theatre or indeed any forum of academic discourse. All academic discourse seeks to explore ideas, often rigorously interrogating their flaws and weaknesses. However, promoting and trying to inculcate ideologies and doctrines is another matter. That and ordinary academic discourse should not be confused.

To that end, I did once have a professor who discussed defecation and its... (left us call them for politeness) concomitants. There is a lot of feedback to be had from the act of defecation. What this tells us about the state of our bowels is important to recognise and should not be ignored out of mere politeness. Bowel cancer has become a prominent topic in the UK in recent years. Now is clearly a time to relax certain inhibitions on what is discussed.

NB As the length of the Wikipedia entry on flatulence demonstrates, there is much more to bowel gas than one realises. I was surprised; it is worth a look.

Cisterna Chyli

I previously mentioned the LOS (Lower Oesophageal Sphincter) and how once it had no place in the human anatomical canon but now does. What of things being the other way round? That is, are there any structures that exist in the human anatomical canon but not in the human body? If there is a candidate, it is the cisterna chyli. This is (supposedly) an expanded portion of the lower end of the thoracic duct where a number of lymph vessels converge, delivering their contents on the way to being returned to the circulation.

The cisterna chyli was first described in the 1650s by Jean Pecquet (1622-1674), a French anatomist whose work relied upon dissections using dogs rather than human cadavers. Notwithstanding this, the cisterna chyli went on to find its way into human anatomy texts. When eponymes were popular, textbooks of human anatomy often referred to it as the 'cistern of Pecquet' or 'reservoir of Pecquet'. There it has remained. However, it is not, in fact, a structure often found in humans.

Studies using human material suggest that the cisterna chyli may only be present in about 14% of individuals. (This I obtain from a footnote to the 35th Edition of Gray’s Anatomy.) A number of variants in the arrangement of the lymph vessels in the area of the lower thoracic duct/cisterna chyli are well known. In fact, the area is often highlighted as being one of considerable anatomical variability.

Surely, if the cisterna chyli is not present in the human body and that area is known for being very variable, how does it persist in the textbooks? Wouldn’t generations of medical students looking for it not point out to their teachers that it wasn’t where they were told to find it?

In my experience, generations of medical students dissecting the posterior abdominal wall and not finding it have blamed their poor dissecting skills rather than the textbooks and dissecting guides. Their teachers have similarly assumed these sources to be unerring and their students clumsy.

If correct, how does an occurance rate of 14% qualify something to be taught as canonical? When performing statistics on experimental data, 95% is the confidence level at which a result is deemed statistically significant. Occurring in the human body at a rate of 14% is well below 95% and hardly implies that it is ‘typical’ or ‘ordinary’… or canonical.

Note on Jean Pecquet

I once read that Pecquet’s particular research interest was the physiological effects of alcohol. In an era when investigators were not averse to experimenting on themselves, it appears that Pecquet did the same… and died of the effects of his own research.

More on Medawar

In a previous post (The Mind of a Human Biologist), I mentioned how Peter Medawar (1915–1987) had provided a foreword for the book entitled Human Biology and had given his opinion as to what it was. Why had the authors agreed to asking Medawar to perform that task?

I suspect that it was something about Medawar that made him the ideal person to write the foreword. He was not simply a prestigious name to be called upon to give a new book cache. He represented something of what a Human Biologist ought to be. He was a Human Biologist before the term became popular. That included him also being something of a philosopher.

He championed the ideas of Sir Karl Popper (1902–1994) and, in particular, the hypothetico-deductive method (or model) of doing science. Philosophy is not a popular discipline among practicing scientists. One reason for this seems to be that scientists view philosophers as speculating without an evidential base, whereas they see themselves as basing their thinking firmly on objective data. Philosophers do not collect data. Instead, they interrogate the thinking that arises from those data.

I suspect that there may also be some degree of prejudice born of interdisciplinary rivalry, which is inculcated into the minds of all young would-be scientists. (Unless, of course, they are strong-willed enough to make up their own minds.)

Medawar not only championed Popper’s ideas; he presented Popper’s hypothetico-deductive system in terms accessible to scientists. They did not have to resort to Popper’s original philosophical writings. This Medawar did through lectures and essays written for a broad audience. His Jayne lectures of 1968, published as ‘Induction and intuition in scientific thought’ (published separately in a slim volume and later collected within Medawar’s ‘Pluto’s Republic'), are a case in point. These are writings accessible to all thinking persons.

Richard Dawkins (1941–) once referred to Medawar as "the wittiest of all scientific writers." Medawar’s scientific writing was certainly not devoid of humour. His ‘Aristotle to' Zoos'—subtitled A Philosophical Dictionary of Biology and co-authored with his wife—was, by all accounts, written amid howls of laughter as he thought of a witty way to put some scientific fact.

For instance, he defined a virus as “a piece of bad news wrapped up in protein.” That phrase describes exactly what a virus is. A proteinaceous capsule containing genetic information (in the form of RNA or DNA) that, when disease-causing, is clearly bad news for those infected. As a definition, it is more memorable than any to be found in any textbook. If called upon to describe a virus, it can readily be translated back into drier (more academically acceptable) scientific terms. (Perhaps only "bad news in a protein coat" can be said to be more concise.)

In the introduction to the final posthumous collection of his essays, their editor, David Pyke, predicted that his work would continue to be read for years to come. That prediction has not come to fruition. Only a few of his books appear to be still in print. One must search for second-hand copies of most of his work. This is pity. His writing is deserving of greater attention. Even if the content is sometimes a little dated, the style and expression of ideas merit consideration.

Interestingly, Medawar never really wrote a book as such. Most of his work published in book form consisted of essays or published lectures. That makes them all the more palatable to scientists. Most scientists deal in facts, pure and simple. As already noted, they are not idle speculators. They don’t want to be encumbered with spurious and unsubstantiated speculation expounded at length. Medawar’s essays do not fall into that trap.

I once heard Medawar speak. He gave an invited lecture at the University of Surrey in my final year as an undergraduate there (1980-81). Having been crippled by a series of strokes, he sat in his wheelchair throughout his delivery. His lack of mobility was in stark contrast to what he had to say. His brain had suffered from the strokes, but his mind was lucid and unimpaired. (Somebody once quipped that the effect of the strokes he had suffered was to reduce his IQ to three digits!) As an undergraduate, I had already discovered his writings because my course in Human Biology had the breadth to allow his ideas to be introduced to us. A decade later, I based a master's dissertation on some aspects of the scientific thought expressed in them.

Soft Machine

In looking at the human body, sometimes non-scientists have something to offer—if only by the turn of a phrase. While writing the previous post on ‘Water,’ I was reminded that a name that has been applied to the human body is the soft machine. Because of our watery nature we are soft and ‘squashy.’

William Burroughs wrote a book entitled The Soft Machine. It is not an easy book to read, and I have failed to get very far into it on a couple of occasions! However, the title continues to be intriguing.