358 ACTIVITY OF THE WALL OF THE ALIMENTARY CANAL. 



stomach also, as well as those of the large intestine, take part in this 

 process. In the villi the fat-granules are seen: (i) Within the epithe- 

 lial cells, the protoplasm of which is dotted with them. The nucleus 

 remains free from them, yet it is so beset by the innumerable fat-granules 

 as to escape observation. (2) Within the tissue of the villus itself, the 

 granules traverse in large numbers the intercommunicating course of the 

 spaces in the reticular tissue. Not rarely, when absorbed in smaller 

 amount, the granules arrange themselves in connected reticular paths. 

 At times they appear to be collected in undivided, band-like lines; at 

 other times, the entire parenchyma of the villus is completely filled with 

 innumerable granules. (3) At a later period the central lymph- vessel 

 in the axis of the villus appears filled with fat-granules. 



The amount of fat in the chyle varies in the dog, after generous 

 feeding of fat, from 8 to 10 per cent. The fat disappears from the 

 blood within thirty hours. If chyle, rich in fat, is mixed with blood 

 (even if lake-colored), and is agitated with air, the amount of fat in 

 the mixture diminishes as a result of the action of a lipolytic substance 

 present in the blood, in consequence of which a body, insoluble in ether, 

 is formed. 



The fat-granules are taken up out of the blood by the various tissues, particu- 

 larly by the liver, and in smallest measure by the muscles. The consumption 

 of fat in the tissues begins with a division into glycerin and fatty acids, which is 

 followed by the final combustion. 



With regard to the forces that effect absorption of the fat-gran- 

 ules, it appeared conceivable from observations made by v. Wisting- 

 hausen that moistening of the porous membranes with bile is capable 

 of facilitating the passage of fat-granules ; but this does not adequately 

 explain the abundant and rapid absorption. It appears most probable 

 that the protoplasm of the epithelial cells of the alimentary tract seizes 

 the fat-granules by an independent movement, and then actively draws 

 them within itself. The protrusion of delicate protoplasmic filaments 

 from the cell-body would take place in a manner similar to that 

 in which the absorption and the inclusion of granular articles of food 

 takes place in the lower organisms, the amoebae. Absorption is possible 

 on the part of the goblet-cells also, because the entrance to the cell 

 remains open. The protoplasm of the epithelial cells communicates 

 directly with the protoplasmic lymphoid cells present in large number 

 within the reticulum of the villus. Thus, the granules may be conveyed 

 to these cells and finally from them, through the stomata between the 

 endothelial cells, into the central lymph- vessel of the villus. 



The process of the absorption of granules and perhaps the same is in 

 part true of proteids is thus established as a wholly active, vital one. 

 This view receives adequate support from the investigations of Briicke 

 and of v. Thanhoffer and others, as well as the observation of Griinhagen 

 that the absorption of fat-granules in frogs takes place most rapidly at 

 a temperature at which the motile phenomena of the protoplasm are 

 most active. In fact, the conception of a simple physical filtration of 

 the granules into the tissue of the villus is scarcely any longer permissible. 

 This is to be concluded also from the fact that the number of fat-granules 

 present in the chyle is independent of the amount of water present in 

 it. If absorption took place essentially through filtration, the constancy 

 of a direct relation between the amount of fat and the amount of water 



