INTESTINAL MUCOUS MEMBRANE. 167 



extent of the small intestine. On examining the sur- 

 face of a piece of mucous membrane under water, 

 with a low magnifying power, we recognise a great 

 number of minute holes, which are nothing more than 

 the orifices of these glands (PL XXVI. fig. II. 4 ; fig. 

 III. 2 ; fig. XII. 3). Their structure has been already 

 studied. 



The ductless follicles, with the structure of which Ductless glands 

 we are already familiar, are either solitary or aggre- 

 gated in groups, and in either case are imbedded in 

 the sub-mucous tissue. As solitary glands, they are 

 scattered throughout the whole extent of the mucous 

 coat of the jejunum and ileum. It is only in excep- 

 tional cases that they are found in the duodenum. 

 When collected in groups they constitute the essen- 

 tial element of the patches of Peyer. These latter, 

 very variable in number, are usually seated in the 

 ileum and lower half of \\\e jejunum y sometimes, but 

 very rarely, they are found higher up, and even in 

 the duodenum. They are oval in shape, with their 

 Long diameters parallel with the axis of the intestinal 

 canal, and are seated opposite to the attachment of 

 the mesentery. The surface of a patch of Peyer is 

 studded with villi, and also with the minute orifices 

 of Lieberkuhn's follicles, as elsewhere on the surface 

 of the intestinal mucous membrane ; but besides these 

 it presents a number of larger depressions (one-half a 

 line in measurement), at the bottom of each of which 

 is a little prominence which corresponds to the posi- 

 tion of a ductless gland. These are perfectly blind 

 depressions, situated just over the glands, and this 

 relation between the two has given rise to the false 



