42 LIEBERKUHN ON THE VILLOUS COAT. 



I 



between these surfaces ; for if a portion of the small intestine 

 be inverted, and then suspended in perfectly transparent water, 

 in a clear glass, and examined with a strong light, it will 

 appear like the external surface of the skin of a peach, on 

 which the down or hair-like processes are not so close as those 

 on velvet. On this surface, between the villi, there are many 

 orifices of mucous follicles and of exhaling vessels.* Exterior 

 to the villous coat, many very sjpall glandular bodies are some- 

 times found, which are called after their describers Glandulae 

 Brunneri and Peyeri. 



The internal coat of the upper portion of the intestinal tube 

 is arranged so as to form a great number of transverse or circu- 

 lar folds or plaits, called Valvula Comiiventes, which do not 

 generally extend round the intestine, but are segments of 

 circles ; they are so near each other, that their internal edges, 

 which are very movable, may be laid upon the folds next to 

 them, like tiles or shingles. It is evident that this arrangement 

 of the internal coat must add greatly to its length. This coat 

 is extremely vascular, so that in the dead subject it can be 

 uniformly colored by ,a successful injection. The minute 

 structure of it has been the subject of very diligent inquiry. 

 There can be no doubt but that an immense number of exhaling 

 and of absorbent vessels open upon it ; but there are many dif- 

 ferent opinions respecting the termination of one set of vessels 

 and the commencement of the other. 



A very interesting account of the Villous Coat was published 

 in 1744, by Lieberkuhn, who was considered by his contem- 

 poraries as a most expert practical anatomist, and was also very 

 skilful in microscopical examinations, for which he was particu- 

 larly calculated, as his natural powers of vision were uncom- 

 monly strong. In his essay he refers to his preparations, which 

 were at Berlin, and which appear to have excited great surprise 



* It appears clearly, from the account of Lieberkuhn, that the orifices or 

 terminations of the arteries on the intestines, are distinct from the follicles ; 

 for he forced injections from the arteries into the cavity of the intestines, and 

 found the follicles still filled with mucus. He then urged the injection further, 

 and filled the follicles, or forced the mucus out of them. 



