494 MANUAL OF HISTOLOGY. 



meshes, whose long axes correspond with that of the contractile elements. 

 The submucosa is from this supplied further with another network of 

 capillary tubes of somewhat greater calibre than the first (Frey). 



The chief supply, however, is to the mucous membrane itself. Here 

 arterial twigs arriving at the bases of the crypts of Lieberkuhn gradually 

 break up into networks of capillaries of medium calibre, with oblong 

 meshes, similar to those of the peptic glands. These are disposed, in the 

 first place, around the mouths of the glands in delicate rings, and then 

 continued into the mesh-work of the villi. The veins arising in the 

 latter, with which we are already acquainted, descend directly downwards 

 through the mucous membrane, receiving but few lateral twigs, and 

 empty themselves into the submucous venous network. 



The presence of racemose glands and lymphoid follicles necessitates, in 

 many parts of the intestinal tract, a modification of this vascular arrange- 

 ment. The well-known round-meshed network, for instance, is met with 

 around Brunner's glands in the duodenum. Then Peyer's patches require 

 a more highly developed vascular system. Here little arteries ascend, 

 either in the septa, or the connecting or junction layer of the follicles, 

 after sending off twigs for the fundus of each of the latter, as well as for 

 their sides. Thus they reach and break up into the terminal capillary 

 network of the ridges and intestinal villi. From thence the blood is 

 taken up by lateral branches of the veins arising here, which descend by 

 the side of the arteries, receiving also an addition from the follicles. 



258. 



Through the exertions of Teichmann, His, Frey, and Auerbach, we 

 have recently become accurately acquainted with the nature of the 

 lymphatic apparatus of the small intestine. This is from many points 

 of view of great interest. 



Its roots have two sources : in the first place, the mucous membrane 

 with its villi, and then the muscular coats of the intestine. The last 

 source was only lately discovered by Auerbach, while the first has long 

 been known, owing to the fact of the vessels here being so distinctly 

 visible when full of chyle. 



A few hours after the reception of fatty food into the stomach, the 

 matters found in the small intestine are found to contain neutral fats in 

 a condition of the most minute division, a physical change brought about 

 by the admixture with tbem of the bile and secretions of the pancreas 

 and mucous membrane of the intestinal tubes. The fats are now in a 

 condition capable of being absorbed, and they are soon taken up in large 

 quantities. In this last process the villi are especially active, if not 

 exclusively so, and principally their apices. 



The commencement of the process is as follows : The fatty globules 

 in the form of extremely minute particles of from 0'0045 to O'OOll mm. 

 in diameter, after passing through the thickened porous border on the 

 epitheliad cells, arrive within the bodies of the latter. At first only a 

 few cells are seen to be filled in this manner, the fatty granules occupy- 

 ing principally that portion of the cell between the nucleus and the free 

 end. The number of cells, however, presenting this fatty infiltration 

 soon becomes greater and greater, and the fat-molecules penetrate past 

 the nucleus into the pointed and attached half of the columnar elements. 

 In the further progress of this process the granules of fat pass through 

 the apices of the cells into the tissue of the mucous membrane beneath, 



