188 LYMPHATIC SYSTEM. 



they look like the valvulse conniventes in miniature, or are small 

 folds of the internal coat : so the accurate Lieberkiihn has 

 painted them. 1 



The whole surface of the alimentary canal is covered with 

 these processes ; but in the large intestines they are so very 

 short, that to 4he naked eye the surface of these intestines 

 appears smooth; thence the learned Albinus has considered 

 them as having no villi, 2 which is true in one sense only, viz. 

 that their inner coat does not appear -shaggy, but spongy or 

 cellular; yet the partitions between these cells are similar in 

 structure to the villi of the small intestines. 



The appearance of the villous coat is very different in dif- 

 ferent parts of the alimentary canal. 



In the oesophagus the villi are small and not so full of ves- 

 sels, and are of the cylindrical or conical shape. 



At the upper part of the stomach the villous coat appears in 

 a microscope like a honeycomb, or like the reticulum, or 

 second stomach of a ruminant quadruped in miniature ; that is, 

 full of small cells, which have thin membranous partitions. 

 Towards the pylorus these partitions are lengthened so as to 

 approach to the shape of the villi of the jejunum. 



The villi of the jejunum are thin folds considerably broader 

 than they are long, and when not injected they, are very flat, 

 so as to resemble valvulse conniventes in miniature, but are so 

 small that they can but just be distinguished by the naked eye. 



In the ileum the villi become rather longer in proportion to 

 their breadth. In the colon and rectum the villous coat is like 

 the upper part of the stomach, honeycombed or cellular. 

 These facts are only evident after a minute injection; for in the 

 uninjected state the villi collapse, so that their figure cannot be 

 distinguished. The partitions between the cells of the internal 

 coat of the colon and of the stomach being each very vascular, 

 and agreeing with the villi of the jejunum in every circum- 

 stance except magnitude, are to be considered as having the 

 same use, namely, to absorb, as will appear probable hereafter. 



Upon each of the villi is an artery and a vein which make 

 a network of branches, as is well expressed in the ingenious 

 Lieberkiihn's plate. 3 



1 De Villis Intestin. tab. i. 2 Annotat. Academic, lib. vi, cap. viii. 



3 De Villis Intestinorum, tab. i, icon. 2. 



