v INTERNAL EESTITUTIVE SECRETIONS 285 



they denied that the whole of the ingested fat was absorbed in 

 this form. The results of their experiments rather led them to 

 conclude that the form in which fat is absorbed varies in different 

 species of animals; although they maintained that the greater 

 part, if not the whole, of the fat is absorbed in a soluble form by 

 the epithelial cells. In this connection they noticed that when 

 fatty acids are dissolved in bile, the alkaline is transformed into 

 an acid reaction ; when dissolved in the filtrate from the intestinal 

 contents of the dog, the acidity increases. If, therefore, the intes- 

 tinal content has an alkaline reaction, the assumption that it 

 contains dissolved free fatty acids to any non-negligible amount 

 may be excluded. They further observed that the small intestine 

 of white rats was alkaline almost throughout its entire length 

 during fat absorption. In the dog, on the contrary, the lower 

 tract of the ileurn only (as a rule) is alkaline, while the larger part 

 of the small intestine gives an acid reaction. In the contents of 

 the latter the dissolved fat is not present exclusively in the form 

 of free fatty acids, but is in the form of soaps as well, showing that 

 it contains more alkali than is required for combination with the 

 inorganic acids, and that this excess of alkali must be combined 

 with the fatty acids. In the last part of the dog's ileum, the con- 

 tents of which give an alkaline reaction like the whole of the small 

 intestine of the white rat, only soaps are present, in solution. 

 Thus in the white rat, according to Moore and Rockwood, the fat 

 is probably absorbed in the form of soaps; in the dog, part is 

 absorbed as fatty acid and part as soap, in variable proportions. 



The importance of the formation of soaps, according to Moore 

 and Rockwood, lies in the fact that they assist the emulsification of 

 the neutral fats. Even if the fats cannot be absorbed in the form 

 of an emulsion it is easy to see how advantageous to digestion and 

 cleavage the emulsification of fat in the intestine must be : it is 

 then reduced to a state of fine division which presents a far larger 

 surface to the action of the lipolytic enzyme. Moore and Rock- 

 wood noted emulsification of fats in the intestine in 10 out of 16 

 experiments on dogs, although never in the degree of fineness and 

 stability characteristic of the milky emulsion present in the chyle. 



In view of the experiments above described, on the effects of 

 extirpating the pancreas and diverting the bile, or of the two 

 operations together, as regards fat absorption, it appears to us that 

 other considerations may be added to the conclusions of Moore 

 and Rockwood as to the importance of soap formation. It is 

 evident that the soaps serve not only to emulsify the neutral fats, 

 and thus supplement the function of the lipolytic enzyme and the 

 bacterial ferments, but also to facilitate probably to render 

 possible the absorption of the digested fats. The waste fat met 

 with in the dejecta (much or little according to the different con- 

 ditions of experiment) always consists mainly of free fatty acids 



