2i6 THE ENGINES OF THE HUMAN BODY 



many kinds of gases. We have noticed that the caecum 

 is always more or less distended with a gas ; a steady 

 volume or cap of air is also maintained in the fundus of the 

 stomach, thus furnishing the left dome of the diaphragm 

 with a cushion of air against which it may work. How 

 are the quantities of air or gas in the caecum and stomach 

 maintained at a constant level when we are in a state of 

 health ? Undoubtedly the amounts are regulated by the 

 activity of the epithelium which lines these chambers. 

 The gases formed during normal digestion in the great 

 bowel are absorbed and transformed by the living units 

 of its pavement. If the pavement units are temporarily 

 damaged, or if the production of gas is excessive from the 

 nature of the alimentary contents or exacerbation of the 

 activity of the ferment-causing organisms, then gas does 

 collect and the bowel becomes uncomfortably distended. 

 One result of distension is to disturb the transport 

 system of the bowel ; the engine spindles in its muscular 

 coats are excited to activity, but find their mechanism 

 ineffective for the transport of gaseous contents. Their 

 efforts are attended by a form of pain with which most 

 human beings become familiar at one time or other, par- 

 ticularly after indiscretions of diet. 



We have just seen that the great bowel is an elabor- 

 ately fitted laboratory ; Nature has spent her most 

 ingenious efforts in its construction. How is it, then, 

 that in recent days the cry has arisen that, so far as man is 

 concerned, the great bowel is a death-trap and that the 

 human race would gain if they lost it ? It is certainly 

 true that it brings misery into the lives of millions of 

 living men and women, and that its derangement is the 

 cause of death in thousands. Metchnikoff and those 

 who share his beliefs throw the blame of these disasters 

 on Nature. Are we quite certain that the fault does not 

 lie with man himself ? Let us look at how man fared in 

 a period which, in the geologist's reckoning, is not a 

 remote one. He depended for his sustenance on the 

 natural products of the wood, moorland, river, sea, and 

 shore. In summer and autumn he had plenty ; in winter 



