572 FEVER'S GLANDS. MUSCULAR COAT. 



are most abundant in the caecum and appendix caeci ; they are small 

 circular projections, flattened upon the surface, and perforated in the 

 centre by a minute excretory opening. 



The Aggregate, or Peyer's* glands, are situated near the lower end 

 of the ileum, and occupy that portion of the intestine which is opposite 

 the attachment of the mesentery. To the naked eye they present the 

 appearance of oval disks, covered with small irregular fissures ; but 

 with the aid of the microscope they are seen to be composed of 

 numerous small circular patches, surrounded by simple follicles, like 

 the solitary glands of the small intestine. Each patch corresponds 

 with a flattened and closed sac, situated beneath the membrane, but 

 having no excretory opening, and the interspace between the patches 

 is occupied by flattened villi. 



The Simple follicles, or follicles of Lieberkiihn, are small pouches of 

 the mucous layer, dispersed in immense numbers over every part of 

 the mucous membrane. 



MUSCULAR COAT. The muscular coat of the pharynx consists of 

 five pairs of muscles, which have been already described. The mus- 

 cular coat of the rest of the alimentary canal is composed of two planes 

 of fibres, an external longitudinal, and an internal circular. 



The (Esopliagus is very muscular ; its longitudinal fibres are con- 

 tinuous above with the pharynx, and are attached in front to the 

 vertical ridge on the posterior surface of the cricoid cartilage ; the 

 uppermost circular fibres are also attached to the cricoid cartilage. 

 Below, both sets of fibres are continued upon the stomach. On the 

 stomach the longitudinal fibres are most apparent along the lesser curve, 

 and the circular at the smaller end. At the pylorus the latter are 

 aggregated into a thick circular ring, which, with the spiral fold of 

 mucous membrane found in this situation, constitutes the pyloric valve. 

 At the great end of the stomach a new order of fibres is introduced, 

 having for their object to strengthen and compress that extremity of 

 the organ. They are directed more or less horizontally from the great 

 end towards the lesser end, and are generally lost upon the sides of 

 the stomach at about its middle ; these are the oblique fibres. 



The Small intestine is provided with both layers, equally distributed 

 over the entire surface. At the termination of the ileum the circular 

 fibres are continued into the two folds of the ilio-caecal valve, while 

 the longitudinal fibres pass onwards to the large intestine. In the 

 large intestine the longitudinal fibres commence at the appendix vermi- 

 formis and are collected into three bands, an anterior, broad ; and two 

 posterior and narrower bands. These bands are nearly one half 

 shorter than the intestine, and give to it the sacculated appearance 

 which is characteristic of the csecum and colon. In the descending 

 colon the posterior bands usually unite and form a single band. From 

 this point the bands are continued downwards upon the sigmoid 



* John Conrad Peyer, an anatomist of Schaffhausen, in Switzerland. His 

 essay, " De Glandulis Intestinorum," was published in 16/7. 



