420 



MANUAL OF HISTOLOGY. 



As to the composition of the lymph glands but little is known. They 

 contain a certain amount of leucin as a product of decomposition, according 

 to Stadeler, and may also, it appears, contain uric acid, tyrosinC?), and 

 xanthin (?) Krause and Fischer state the specific gravity of the organs 

 in question to be 1*014 in the human being. 



227. 



N early related to the organs we have just been considering, we find 

 others which consist partly of single follicles, and partly of a number of 

 the latter crowded together closely, and held thus by a peculiar connect- 

 ing substance. These are mostly situated in the mucous membranes or 

 submucous tissue. Among these may be reckoned, as occurring in the 

 human being and mammalia, the so-called trachoma glands or lymphoid 

 follicles of the conjunctiva, the lingual follicular glands, and tonsils, cer- 

 tain irregularly occurring follicles of the gastric mucous membrane (lenti- 



Fig. 411. Vertical section of a Peyerian gland Fig. 412. Reticular sustentacular 



from the small intestine of the rabbit, a, tissue between the follicles of the 



villi ; 6, c, follicles. vermiform appendix of the rab- 



bit, 1. Deeper portion in hori- 

 zontal section, a, framework; 

 6, lymph canals. 2. Superficial 

 portion ; a, 6, as in 1 ; c, depres- 

 sion in the mucous membrane 

 lined with cylinder epithelium. 



cular glands), and the solitary and agminated glands of the intestine, 01 

 PC-yen's patches (fig. 411). 



That large massive organ, the thymus, may also be mentioned as pre- 

 senting a similar structure. 



This whole group, including the lymphatic glands themselves, may be 

 named with propriety the group of lymphoid organs. In addition to them 

 we have, finally, the spleen, though no doubt a modified form. 



In all those .organs first mentioned, which belong to the mucous mem- 

 branes, we find the follicle as the essential structure. It corresponds in 

 its structure to the analogous elements of the lymphatic glands, and con- 

 sists of a reticular substance enclosing lymph corpuscles (comp. fig. 400 

 and 412). This presents not unfrequently in its interior a loose and open- 

 meshed appearance, whilst more superficially the network becomes denser, 

 and further outwards still, on the surface, exceedingly close, just as we 



