SECT. 153.] FUNCTION OF THE VILLI IX ABSORPTION. 329 



Briioke affirms, that the central chyle-vessel of the villi is a space without 

 bounding walls, ami that interstitial depositions of chyle also take place in 

 other parts of the mucous membrane, and are then conveyed onwards into 

 the true chyle-vessels. I, on the other hand, hold that the chyle-trunk of 

 the villus possesses a membrane, which I have distinctly seen, and believe 

 that Briicke has been led to his view, more from theoretical considerations 

 than from direct facts. Similar considerations have induced this author 

 to assert, that the epithelial cylindrical cells of the villi are completely 

 destitute of a membrane at their broader extremity, and have orifices at the 

 part turned towards the villus, to which similar openings in the limiting 

 membrane of the villus itself correspond. Brucke himself admits that the 

 two last-mentioned openings cannot be directly observed, so that I shall 

 content myself with remarking, that, according to my most recent investi- 

 gations (Li. a), there can be no doubt as to the existence of a membrane 

 on the free extremity of the cells. By Briicke's view, the difficulties which 

 present themselves in explaining the absorption of fat, would, undoubtedly, 

 be easily removed, if apertures were demonstrated to exist everywhere ; 

 but this can furnish no reason to disregard undoubted facts. In the 

 absorption of fat, as Goodsir, and Gruby and Delofoud have shown, the cylin- 

 drical epithelial cells, — frequently on the whole of the villus, but often 

 only on the apex (because the villi, when they are distended and the intes- 

 tine is contracted, frequently lie so close to each other, that only their apices 

 are accessible to the intestinal contents) — become filled with fine fat-granules 

 or larger fat-drops, but how, is still undetermined. 



According to the most recent investigations of Brucke and myself, the fat, 

 before its absorption, divides into molecules of immeasurable fineness, and 

 it is taken up only in this form by the epithelial cells. Now, since I have 

 shown that these cells possess a distinct and even thickened membrane 

 upon their surface which is directed to the intestinal canal, we are com- 

 pelled to assume, that the fat-molecules pass through this membrane, either 

 by preformed canals or pores, or by making a way for themselves through 

 the substance of the membrane. With regard to the existence of pore- 

 canals in the cell-membranes in question, I refer the reader to my treatise 

 cited above, and remark here only this much, that it is very possible, that 

 the strice discovered by me in the cell-wall are to be attributed to extremely 

 fine canals. At any rate, these stripe point to a quite peculiar structure of 

 the absorbing cell-walls, and deserve, accordingly, a special consideration on 

 the part of physiologists. I may add, that the thickened striated cell-wall 

 swells up in water, and suffers a peculiar splitting, so that it gradually be- 

 comes similar to a bundle of short fibrils or cilia. Such epithelial cells were 

 incorrectly described, a considerable time ago, by Gruby and Ddufund, as 

 ciliated epithelium of the intestine. Danders and I have found that the 

 cyliudrical cells of the intestine not unfrequently burst at their apices, 

 and allow a part of their contents (mucus) and their nucleus to pass out. 

 A second, previously formed cell-nucleus then serves for the regeneration 

 of these cells, which, in this stage, possess opaque, often granular, contents, 

 and clavate forms : these are the cells designated by Gruby and Delafond 

 ' epithelium capitatum.' 



[n the parenchyma of the villi, there are found at the apices frequently 



