LYMPHOID ORGANS. 221 



known lymphatic glands, which are of a certain size, a 

 great number of smaller apparatuses exist in the body 

 which possess precisely the same structure, but do not 

 exhibit such a complex arrangement as we find in a 

 lymphatic gland. To this class belong above all the fol- 

 licles of the intestines, both the solitary and the Peyerian. 

 A Peyer's patch is nothing more than a lymphatic gland 

 spread out as it were upon the surface ; the individual 

 follicles of the patch, just as the solitary follicles of the 

 digestive tract, correspond to the individual follicles of a 

 lymphatic gland, only that the former, in man at least, 

 are disposed in a single layer, the latter in several. The 

 solitary and Peyerian glands have therefore nothing at 

 all in common with the ordinary glands which pour their 

 secretions into the intestinal canal ; on the contrary, they 

 rather hold the position, and manifestly also fulfil the 

 functions, of lymphatic glands. 



To the same category belong in all probability also 

 the analogous apparatuses which we find grouped to- 

 gether in such large masses in the upper part of the 

 digestive tract, where they form the tonsils and \he, folli- 

 cles of the root of the tongue. Whilst in the intestine the 

 follicles lie spread out on an even surface, in these parts 

 the surface is inverted and the individual follicles lie 

 around the involuted membrane. 



To the same category belongs moreover the thymus 

 gland, which in its interior exhibits no other differences 

 of structure excepting that the aggregation of the folli- 

 cles reaches a still higher degree than in the lymphatic 

 glands. Whilst in most of the lymphatic glands we have 

 a hilus, where there are no follicles, this ceases to be the 

 case in the thymus gland which has no hilus. 



Finally, to the same class belongs also a very essential 

 constituent of the spleen, namely, the Malpighian or white 

 bodies, which in different persons are distributed in just 



