488 THE SOLIDS. 



of the jejunum that they are best developed, and the lacteals 

 most readily detected. 



Several distinct structures have to be noticed and described 

 entering into the constitution of each villus : these are the 

 epithelium resting upon the outer surface of the villus, the 

 basement membrane, the intra-villous nuclear contents, the 

 fatty intra-villous contents, the blood-vessels of the villus 

 and its lacteals ; these several parts will be described in the 

 order of their enumeration. 



The epithelium investing the villi (see Plate LIT. Jig. 1.), 

 is of the conoidal variety already fully described and figured. 

 It not merely clothes the villi from base to summit ; but 

 also the interspaces between them, as well as the numerous 

 follicles of Lieberkuhn, situated in the whole length of the 

 small intestines. 



According to the observations of Professor Goodsir, this 

 epithelium is shed on each recurrence of the process of 

 chymefication, the cells first absorbing the partially elabor- 

 ated chyme, effecting a further elaboration of it, and finally 

 becoming ruptured and dissolved, set free the fluid absorbed, 

 at the same time adding their own substance to augment its 

 amount and nutritive qualities. 



The accuracy of this view is in the main admitted by 

 most observers ; Professor Weber and Dr. Jones, however, 

 do not consider that the shedding of the epithelium is neces- 

 sary to enable the villi to perform their function ; and the 

 latter observer makes the following remarks on this point : 

 " I have certainly seen the villi clad with their epithelium 

 when the lacteals have seemed to be every where filled 

 with chyle : however, I think there can be little doubt that, 

 when the absorbing process is most actively performed, the 

 villus does throw off its protecting covering ; certainly, this 

 is the case in a great number of instances." 



The basement membrane of the villi is a continuation of 

 that of the general surface of the mucous membrane, and is, 

 as far as has yet been ascertained, perfectly structureless. 



* Medical Gazette, Nov. 17th, 1848. 



