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MANUAL OF HISTOLOGY. 



exceptions, especially in the occurrence of isolated Peyer's glands in the 

 colon. 



The vermiform appendix of man, and to a greater extent also that of 

 the rabbit, may likewise be said to be one large Peyer's gland, composed 

 of crowded follicles (Teichmann, His, Frey). 



The number of these agminated glands to be found in the human small 

 intestine varies from 1 5 to 50 and upwards. The diameter of such a group 

 cannot, of f course, be definitely laid down, varying, as it does, from 7 mm. 

 to several centimetres. The form they assume is usually oval, their long 

 axis corresponding with that of the intestine. 



Subjecting the glandulce agminatce to close inspection, we find in 

 longitudinal sections that, although the form of the follicles may be 

 similar in one and the same group, nevertheless it is liable to vary to a 

 large extent, both in different animals, and according to the locality in 

 the intestine we choose for examination. 



Beside spheroidal follicles, namely (fig. 483), we meet with others more 

 or less elongated, presenting somewhat the figure of strawberries. But in 

 other instances the follicles maybe so increased in vertical diameter as to 

 present on section an outline resembling that of the sole of a shoe. In 



Fig. 483. Vertical section of one of Peyer's plaques from man, injected through its lymphatic canals 

 a, villi, with their chyle passages; b. follicles of Lieberkuhn; c, muscularis of the mucous membrane; 

 d, cupola or apex of follicles; e, mesial zone of follicles; /, base of follicles; g, points of exit of the 

 chyle passages from the villi, and entrance into the true mucous membrane; ft, retiform arrange- 

 ment of the lymphatics in the mesial zone ; i, course of the latter at the base of the follicles ; k. 

 confluence of the lymphatics opening into the vessels of the submucous tissue; I, follicular tissue of 

 the latter. 



man they are usually of the spheroidal kind ; in the small intestine of 

 the rabbit strawberry shaped. Those very much elongated examples just 

 mentioned are to be found chiefly in the under portion of the ileum of 

 the ox and vermiform appendix of the rabbit. 



The follicle, however, may be of what shape it will, we can always 

 distinguish three portions in it, namely, the summit or cupola, the mesial 

 zone, and the base. The cupola (d) projects into the intestinal tube ; 

 the base (/) descends to a greater or less depth into the submucous 

 connective-tissue ; and the mesial zone (e) serves to connect together all 



