160 STUDENTS HISTOLOGY 



and there in the mucous coat. These are the lymphatic nodules 

 alluded to above the so-called solitary glands. One of the nodules 

 is indicated in the diagram at I, with its point projecting between 

 the villi at F. 



Continuing your examination of the gut, you will discover, 

 especially in the ileum, roughened patches perhaps five to ten 

 centimeters long by one to two centimeters broad. These are 

 collections of the lymphatic nodules described in the last para- 

 graph, -and are termed agminate glands, or patches of Peyer. They 

 have no secretive power, being simplj' in connection with, and a 

 part of, the chain of lymphatics in the walls of the intestine. They 

 consist of lymphoid or adenoid tissue, which will be described 

 with the lymphatics. 



To recapitulate, the small intestine presents the following: 



1. The mill , each containing a plexus of blood -capillaries and 

 the lymphatic or absorbent vessel. 



2. Crypts or follicles of LieberkUhn. 



3. Brunner's glands. 



4. Solitary lymphatic nodules, the so-called solitary glands. 



5. Agminate lymphatic nodes, agminate glands or patches of 

 Peyer, consisting of aggregations of lymphatic nodules similar to 

 the solitary lymph -follicles. 



The muscular part of the intestine is arranged not unlike that 

 portion of the stomach: i. e., with an inner circular and an outer 

 longitudinal layer. Between the two is located Auerbach' s plexus 

 of non-medullated nerves. A similar plexus, Meissner's, is found 

 in the submucosa. The ganglia may rarely be seen in ordinary 

 sections. 



A small quantity of areolar tissue connects the external longi- 

 tudinal muscular layer with the peritoneal investment. 



PRACTICAL DEMONSTRATION 



The intestines of the dog or rabbit are more commonly used for practical 

 work, for reasons already alluded to. The tissue should be cut into small 

 pieces, and hardened quickly in alcohol. When human intestine can bo 

 obtained fresh, a piece, say three inches long, should be emptied of its con- 

 tents, filled with alcohol by tying the ends, and the whole hardened in strong 

 spirit. Under no circumstances should the gut be washed, and great care must 

 be taken to avoid injuring the delicate cells covering the villi. Vertical sec- 

 tions with the microtome are the most valuable. Stain with hsematoxylin and 

 eosin, and mount permanently in balsam. 



