134 THE BODY AT WORK 



fatty acids are carried into the cells in solution in bile. But 

 if in carnivora bile actively participates in the absorption of 

 fat, there is no reason opposed to its having the same function 

 in Man ; and, indeed, all observations which have been made 

 upon patients in whom the bile was, for some reason, diverted 

 from the intestine, and in animals in which a fistula of the 

 gall-bladder has been artificially produced, show that in the 

 absence of bile the absorption of fat is considerably decreased. 

 Yet there is no reason for thinking that bile is secreted for 

 the purpose of facilitating the absorption of fat. Just as much 

 bile is poured into the intestine of a cow which is feeding upon 

 grass as into the intestine of a pig or a dog when the animal is 

 consuming a very large quantity of fat. Nevertheless, it 

 appears to be certain that, not in carnivorous animals only, 

 but also in herbivorous animals, the assistance of bile is 

 necessary for the satisfactory absorption of fat. Doubtless 

 the co-operation of bile and pancreatic juice is more important 

 to carnivora than it is to herbivorous animals, in which, owing 

 to the alkalinity of the contents of the intestine, all fatty acids 

 liberated by the action of pancreatic juice might be converted 

 into soluble soaps. 



The problem of the form in which foods enter the absorbing 

 cells is intimately associated with the further problem of the 

 form in which they leave them. In the villus, and even within 

 the epithelial cells, fat appears abundantly as such. If, as we 

 have reason for believing to be the case, it enters in the form 

 of soap and glycerin, the reformation of fat is an illustration 

 of the synthetic power of the tissues. For the purposes of 

 the economy it is needed as fat, and not as the constituents 

 of fat. There is no reason for thinking that at any stage 

 in its future progress it is again split into fatty acid and 

 glycerin. 



We cannot see absorbed proteins with the microscope, as 

 we can see fat, nor can we apply chemical tests which will 

 distinguish between the proteins which the cells contained 

 before digestion commenced, and the proteins which they have 

 received as its result. Nevertheless, it is certain that 

 peptones are reconverted into proteins as soon as they are 

 absorbed. They are not to be found in blood or lymph. If 

 the peptones absorbed after a proteid meal remained as such 



