104 SPECIAL HISTOLOGY. 



merit, Frei and Ernst have demonstrated the existence of 

 numerous, but very fine blood-vessels of 0'0015 — 0-004'", 

 which are connected with a rich vascular network surrounding 

 the follicle, and may be readily recognised in the contents of 

 the follicles of animals (Pig, e. g.), if they be quite fresh, and 

 have been extracted with care. 



Little is known of the lymphatics of Peyer's patches. This 

 much is certain, however, that the number of lacteals which may 

 be traced during digestion from the Peyerian patches, is greater 

 than that in other parts of the intestine, although their villi are 

 fewer and less developed ; on the other hand, we know nothing 

 of the internal relations of these vessels. They would seem to 

 form networks around the separate follicles, at least we see 

 that they encompass them externally ; but they do not be- 

 come inserted into, nor enter them, at any rate upon this 

 surface, as their milk-white colour would render their detection 

 easy. Although, then, Briicke has recently affirmed the direct 

 communication of the follicles with lymphatics, I must, for 

 these and other reasons (see Mikr. Anat. II. 2, p. 188), at pre- 

 sent doubt the fact. 



The solitary follicles [glandules solitaries) resemble the sepa- 

 rate elements of Peyer's patches so closely in size, contents (I 

 have also seen the internal vessels in them), 

 and general structure, that there is no 

 reason for considering them as distinct, par- 

 ticularly since the number of the follicles 

 is subject to all possible varieties ; and since, 

 in animals at least, we find Peyer's patches 

 with 2 — 3 — 5 follicles. In man, as all 

 writers justly agree, their number is ex- 

 ceedingly inconstant ; sometimes not one can be found, whilst 

 in other cases, the whole intestine, as far as the margins of 

 the ileo-csecal valve, is thickly beset with them, or lastly, 

 they may occur in the ileum and jejunum, but in no very 

 great number. Their entire absence must probably be 

 considered abnormal, since they are constant in newly-born 

 children, being more abundant in the jejunum than in the 

 ileum. The miliary vesicles, however, which are often met 



Fig. 216. A solitary follicle, covered with villi, from the small intestine. After 

 Bo Inn. 



