284 PHYSIOLOGY CHAP. 



To us, the most interesting fact is that under such conditions 

 fat absorption should still be possible. Analysis of the faeces 

 showed that non-emulsified fats (diet of bacon and meat) were 

 absorbed to an amount of 10 per cent ; finely emulsified fats (milk- 

 diet) were absorbed in quantities above 22 per cent. The greater 

 part of the fats eliminated with the faeces (78-90 per cent) appeared 

 in the form of free fatty acids, which were unmixed with soaps, or 

 mixed to a minimal extent only. There was thus a cleavage of 

 fats to an extent not less, but even somewhat greater, than that 

 which took place in dogs with a simple fistula of the gall-bladder, 

 which gives some idea of the fermentative activity of the intestinal 

 bacteria during the fat digestion. The putrefactive phenomena 

 (apparent in the foetid odour of the excrements), which increased 

 during the course of the observations, appear to be in ratio with 

 the cleavage of the fatty substances. 



In explanation of the intestinal haemorrhage which hastens the 

 death of animals thus operated on, Hedon holds that bile and 

 pancreatic juice have a beneficent action upon the nutrition of the 

 intestinal mucous membrane ; but this is not the place in which 

 to discuss his hypothesis. The important point in his conclusions 

 is that the non-absorbed fats reappear in the faeces mostly in the 

 form of free fatty acids, with few or hardly any soaps. Hedon, 

 with little foundation, considers this fact to be an argument in 

 support of the theory that the cleavage of fats is not a necessary 

 condition of their absorption. We shall see that there is a better 

 interpretation of his significant discovery. 



Another fact, which shows plainly that the glycerides in order 

 to be absorbed must first be decomposed, and then reconstituted 

 by synthesis after absorption, appears from the experiments of 

 Otto Frank (1894), which show that on feeding dogs with neutral 

 fats, or with fatty acids which have a higher melting-point than 

 that of the body (45 C.), they can be absorbed, and that a fat is 

 constantly present in the chyle, which melts approximately at 

 body temperature. On the other hand, it was shown by I. Munk 

 that after ingestion of spermaceti (palmitate of cetyl alcohol) 

 palmitin appeared in the chyle. The cetyl-palmitate therefore 

 splits up, and the palmitic acid combines with glycerol to form a 

 neutral glyceride. Nothing, however, is known as to the origin of 

 the glycerol required in this synthesis. 



After the doctrine of fat absorption as an emulsion had been 

 overthrown, it still had to be decided whether the fats were 

 absorbed in the form of soaps, or of fatty acids, which, as we know, 

 are readily dissolved in bile, and specially in the bile acids (see 

 p. 220). From a series of exact experiments on the solubility 

 of fatty acids in bile (from ox, sheep, or dog) Moore and Rockwood 

 (1897) concluded that this was sufficient to explain the absorption 

 of alimentary fats in the form of free dissolved fatty acids. But 



