320 DIGESTION. 



by anatomists. In one of these varieties, the patch is quite 

 prominent, its surface being slightly raised above the general 

 mucous surface, while in the other, the surface is smooth, 

 and the patch is distinguished at first with some difficulty. 

 The more prominent patches are covered with mucous mem- 

 brane arranged in folds something like the convolutions on 

 the surface of the brain. The valvulse conniventes are ar- 

 rested at or very near their borders. These are the only 

 patches which are generally described as the glands of Peyer ; 

 the others, which may be called the smooth patches, being 

 generally overlooked. The latter are covered with a smooth, 

 thin, and closely adherent mucous membrane. Their follicles 

 are small and numerous. The borders of these patches are 

 much less strongly marked than those of the first variety. As 

 they are evident only upon close examination, and as they 

 are the only patches present in certain individuals, it is said 

 that sometimes the patches of Peyer are entirely wanting. 

 They are generally less numerous than the first variety, and, 

 according to Sappey, are most abundant in persons of feeble 

 constitution. 1 The villi are very large and prominent on the 

 mucous membrane covering the first variety of Peyer's 

 patches, especially at the summit of the folds. In the sec- 

 ond variety, the villi are the same as over other parts of the 

 mucous membrane, except that they are placed more irreg- 

 ularly and are not so numerous. 



The intimate structure of these bodies has not been defi- 

 nitely settled in all its particulars. It is well determined, 

 however, that the follicles which compose them are com- 

 pletely closed ; the openings which have been said to exist 

 being undoubtedly accidental ruptures made in preparing 

 the specimen for microscopic examination. These follicles 

 are somewhat pear-shaped, with their pointed projections 

 directed toward the cavity of the intestine. Just above 

 the follicle, there is generally a small opening in the mu- 

 cous membrane, surrounded by a ring of intestinal tubules, 



1 SAPPEY, op. cit., tome iii., p. 175. 



