THE ABSORPTION OF THE REDUCED FOODSTUFFS 1033 



mucosa contains more ammonia than any other tissue, and that the 

 blood of the mesenteric veins contains from 6 to 10 times as much 

 ammonia as that of other veins. 



In man practically all the proteins are taken in as insoluble com- 

 pounds, or are rendered so by the process of cooking. Their absorp- 

 tion, therefore, necessitates their first being brought into solution and 

 this end is attained by hydration and the action of the different pro- 

 teolytic enzymes. Certain evidence is also at hand to show that a 

 certain proportion of the protein may be absorbed before it has ac- 

 tually reached its final stage of cleavage. Thus, it has been mentioned 

 above that the proteins of blood-serum are eventually taken up; in 

 fact, Friedlander states that as much as 21 per cent, of white of egg 

 may be absorbed by washed small intestine in the course of three 

 hours. Syntonin and casein, on the other hand, are not absorbed. 

 Furthermore, patients fed per rectum with protein material, are capa- 

 ble of absorbing a considerable portion of it, although proteolytic 

 enzymes are not present in this segment of the intestine. It is also a 

 matter of common experience that certain persons may develop an idio- 

 syncrasy or anaphylaxis against the proteins of milk and white of egg, 

 which is due in all probability to the absorption of protein in its more 

 complex form. We are justified, however, in concluding that, under 

 perfectly normal conditions, the absorption of only partially reduced 

 protein is the exception. 



Besides the increase in the number of the leukocjrtes, it has been 

 noted by Renter that the cells of the villi become swollen when protein 

 absorption is going on. Furthermore, their cytoplasm does not stain 

 deeply at this time, owing, in all probability, to the accumulation of 

 a hyaline coagulable material. 



B. ABSORPTION FROM THE CAVITIES OF THE BODY 



Absorption from the Peritoneal Cavity. — In the intestine, the body- 

 fluids are separated from the liquefied foodstuffs by a layer of colum- 

 nar epithelium which owing to its depth, is capable of influencing 

 diffusion in an active manner. The body-cavities, on the other hand, 

 are lined with only a thin sheet of endothelial cells, and hence, we 

 might expect in this case a preponderance of the physical forces. 

 While these functional differences no doubt exist, the fact still remains 

 that the endothelial cells are by no means perfectly passive entities. 

 We have really come to this conclusion on previous occasions, while 

 discussing the part played by the glomerulus in the formation of urine 

 and the function of the endothelium of the blood capillaries in the pro- 

 duction of lymph. As far as the lining of the pleural and peritoneal 

 cavities is concerned, it has been noted repeatedly that pleural and 

 ascitic effusions may be reabsorbed in the course of time, provided 

 the cause leading to these extravasations has ceased being active. 



