296 DIGESTION. 



without being saponified when they were saturated with such fluids 

 as a solution of soap or bile. 



Even if these experiments cannot be considered as having 

 entirely elucidated all the conditions affecting adhesion, they place 

 it beyond a doubt that the presence of bile is essentially necessary 

 for the resorption of fat, since this fluid renders these delicate mem- 

 branes permeable by the fat. It is, however, obvious, that if the 

 membrane or cell- wall be once saturated with a bilio-oleaginous 

 fluid, it will the more readily permit the passage of more fat, and 

 consequently, that the inequality in the filling of the individual 

 vesicles either with fat or with a granular aqueous fluid admits of a 

 very ready explanation. These differences may, however, manifest 

 themselves more in the outer portion than in the interior of the 

 villi, since the pressure which at intervals is exerted by the organic 

 muscles of the villi on the interior, obviously contributes very much, 

 as von Wistinghausen's experiments show, to the intimate admix- 

 ture of the oil and the aqueous fluid, which must, therefore, take 

 place at the very commencing points of the lacteals. 



If, as we learn from Bidder and Schmidt's experiments, a small 

 fraction of the fat is resorbed, even without the co-operation of the 

 bile, this is to a certain degree explained by the subsequent expe- 

 riments of von Wistinghausen, even if we are unable specially 

 to indicate the exact pressure or the exact substance which effects 

 the transition of this small quantity of fat. 



After the preceding remarks it is obvious that no further proof 

 is required that the fat is principally resorbed by the lacteals. It 

 must, however, be obvious from Schmidt's and my own observa- 

 tions (vol. ii, p. 247), that the capillaries also take up fat, although 

 in less considerable quantities ; for the augmentation of fat which 

 we observe in the portal blood of animals a few hours after they 

 have been fed, cannot with any probability be explained by such an 

 assumption as that the carbo-hydrates resorbed by the intestinal 

 capillaries become converted into fat in their passage from the 

 intestinal cavity to the portal vein. The above-mentioned obser- 

 vation of Bruch's, who saw fatty chyle- like masses beside blood- 

 corpuscles in the capillaries of the villi, seems (as there does not 

 appear to be any possibility of error in the observation) to afford 

 the most distinct proof that there is a direct transmission of fat 

 into the blood of the capillaries from the epithelial cells and the 

 parenchyma of the villi. 



We now proceed to that group of substances which must 

 undergo an essential change in the intestinal canal before they are 



