288 THE DIGESTIVE ORGANS. 



baskets have also been observed in the ganglia of the plexuses of 

 the stomach and esophagus. Large medullated nerve-fibers, the 

 dendrites of sensory neurones, have also been traced to the alimen- 

 tary canal. In the esophagus these pass to the mucosa, where, 

 after repeated division, they lose their medullary sheaths, the non- 

 medullated terminal branches forming a subepithelial plexus from 

 which terminal, varicose branches, further dividing, enter the strati- 

 fied epithelium and may be traced to near the surface of the epithe- 

 lium. 



Large medullated nerve-fibers may be traced through the 

 ganglia of Auerbach's and Meissner's plexuses in the stomach and 

 intestinal canal and through the nerve bundles uniting these ganglia 

 (Dogiel, 99), but the termination of these fibers has not been deter- 

 mined. In the large intestine of the cat they have been traced to 

 the epithelium and between the epithelial cells covering the mucosa 

 (Huber). 



6. THE SECRETION OF THE INTESTINE AND THE ABSORPTION 



OF FAT. 



The cells of Brunner's glands are similar in many respects .to 

 those of the pyloric glands. They form, as has been shown, a 

 mucous secretion, and present in their various physiological activi- 

 ties, structural changes which are similar to the structural changes 

 presented by the cells of other mucous glands under similar condi-- 

 tions (Bensley). It is well known that the goblet cells of the in- 

 testinal glands are very numerous during starvation, and that they 

 nearly disappear after continued functional activity ; furthermore, 

 they entirely disappear in certain portions of the rabbit's intestine 

 after pilocarpin-poisoning. It would therefore appear that the prin- 

 cipal physiologic function of the glands of Lieberkiihn is to secrete 

 mucus, although the possibility of the production of another secre- 

 tion, especially in the small intestine, must not be excluded (compare 

 R. Heidenhain, 83), especially since it has been shown that the 

 cells of Paneth probably elaborate an enzyme. 



Until recently it was believed that the fat contained in the food 

 was emulsified in the intestine, and furthermore that the bile acted 

 upon the cuticular margins of the epithelial cells in the villi in such a 

 manner that an assimilation of the emulsified fat by the cells of the 

 villi (not by the goblet cells) was made possible. It has been re- 

 peatedly observed that the epithelial cells contained fat granules 

 during absorption. Hence a mechanism was sought for which 

 would account for an assimilation of globules of emulsified fat on 

 the part of the cells. It seemed most probable that protoplasmic 

 threads (pseudopodia) were thrown out from each cell through its 

 cuticular zone, which, after taking up the fat, withdrew with it again 

 into the cell. But when it was shown that, after feeding with fatty 

 acids or soaps, globules of fat still appeared in the epithelial cells as 

 before, and that the chyle also contained fat, the hypothesis was 



