358 



described as depressed into a fossa in this 

 situation. The thin stratum of tissue which 



270. 



STOMACH AND INTESTINE. 



Plan of an agminate follicle, as seen by a vertical 

 section. Magnified 40 diameters. 



a, short and conical villi surrounding the follicle ; 

 b, intestinal tubes in the same situation ; c, muscu 

 lar stratum of the mucous membrane ; d, submu- 

 cous areolar tissue, in which the follicle is chiefly 

 situated ; e, circular layer of the muscular coat ; 

 /, longitudinal layer of the same ; g, peritoneal coat ; 

 h, follicle enclosing nuclear contents ; z, apex of the 

 follicle projecting into the cavity of the bowel. 



intervenes between the follicle and the interior 

 of the bowel (at i,fig. 270.) is so delicate, 

 that its exact anatomy is not easily verified by 

 vertical sections. It appears, however, to con- 

 sist of a very small quantity of indistinctly 

 fibrous tissue ; which encloses some capillaries, 



and is covered by the ordinary layer of co- 

 lumnar epithelium. 



The frequent rupture of the follicle in this 

 situation has led many to regard it as either 

 possessing a permanent orifice here, or ac- 

 quiring one by a kind of natural dehiscence. 

 But later researches seem to show that this open 

 state is quite exceptional and accidental ; being 

 due to disease, putrefaction, or mechanical 

 violence. The author can at least express 

 his own conviction that as Boehm long ago 

 stated, the agminate follicles are closed sacs. 

 This conclusion is much confirmed by the 

 fact, that the follicles of some animals are 

 altogether beneath the mucous membrane and 

 the tubes, and quite distinct from both of 

 them ; so as to lie wholly in the sub-mucous 

 areolar tissue.* While the vascular arrange- 

 ments which we are about to describe seem 

 equally incompatible with any theory of their 

 normal dehiscence. 



Each of these follicles essentially consists 

 of a capsule, enclosing a number of delicate 

 capillaries, the interstices of which are occu- 

 pied by a cell-growth consisting of various 

 forms. 



The capsule is a structure which, though 

 analogous to a basement membrane, differs 

 from such a delicate homogeneous lamina, both 

 in being much thicker, and in offering an in- 

 distinctly fibrous texture. Its smooth outer 

 surface contains elastic fibres, and is attached 

 by loose areolar tissue to the surrounding 

 sub-mucous structures. 



The vessels of the follicle offer a very 

 peculiar arrangement. The small arteries in 

 the sub-mucous areolar tissue give off branches 

 that ramify amongst the several follicles of 

 each "patch;" and thus form a network of 



Fig. 271. 



Vessels of the three agminate follicles of the Rabbit ; as seen by a horizontal section, at about the middle of 



their height, (^fter Koelliker ; from an injection by Fret.') 



a, , minute vessels surrounding the capsule of the agminate follicles ; b, b, b, delicate capillary loops 

 , penetrating their interior, and bending back from c, c, c, the centres of the follicles. 



capillary arteries, chiefly occupying the hori- contact with the capsule of the follicle, break 

 zontal plane. These vessels, which are in * Compare Koelliker, Op. tit. pp. 153. 188. 



