LYMPHOID ORGANS. 



387 



the trabeculse are almost or entirely absent, and the interior of the gland then looks 

 in section like a continuous mass of lymphoid tissue, traversed by lymphatic channels. 



It is not unreasonable to presume that, in the proper glandular substance, there 

 is a continual production of lymph-corpuscles, which pass into the lymph-sinus, 

 and that fresh corpuscles are thus added to the lymph as it traverses the gland. 

 This view is supported by the fact, that the corpuscles are found to be multiplying 

 by karyokinesis within the pulp, and are more abundant in the lymph or chyle 

 after it has passed through the glands. 



Other organs composed of lymphoid tissue. Bodies which are similar in 

 structure to lymphatic glands in so far that they are composed of a delicate retiform 

 tissue, the interstices of which are closely packed with lymphoid cells, and are in 

 intimate relation with the lymphatic vessels of the part, occur in many places. 

 Thus, in the serous membranes, rounded nodules are here and there met with, 

 which, as Klein has shown, are developed either around or at one side of an en- 

 larged lymphatic (perilymphangial nodule, fig. 446, A), or in some cases even within 

 the vessel (endolymphanyial nodule, fig. 446, B). The retiform tissue which con- 

 stitutes the framework of the nodule is connected with the wall of the lymphatic, 

 and lymphoid cells accumulate in the interstices of the retiform tissue, where they 

 multiply and ultimately form a dense mass of lymphoid tissue. 



The endolymphangial nodules, although small and simple in structure, closely 

 recall the structure of one of the cortical nodules of a lymphatic gland ; for a path 



Fig. 446. DEVELOPING LYMPHATIC (LYMPHANGIAL) NODULES, FROM THE OMENTUM OF A GCINEA-PIQ. 



(Klein.) 



A, perilymphatic nodule ; a, lymphatic vessel ; c, part of its epithelial wall, seen in optical section ; 

 e, lymph-corpuscles within the vessel : b, lymphoid tissue of the nodule ; d, blood-capillaries. B, endo- 

 lymphatic nodule ; a, vein ; b, artery ; c, capillaries ; d, a lymphatic vessel, in which this whole 

 system of blood-vessels is inclosed ; e, lymphoid tissue within the lymphatic vessel ; f, wall of the 

 lymphatic in optical section. 



or channel for the passage of lymph is left between the central accumulation of 

 lymphoid tissue and the wall of the vessel, this path being bridged across by 

 retiform tissue and branched cells ; and along it the lymph must pass very slowly, 

 and come into intimate relation with the tissue of the nodule. In other cases the 

 lymphoid tissue of the serous membranes is less circumscribed, occurring in the form 

 of ill-defined patches or elongated tracts, which lie along the course of the small 

 arteries and veins, receiving from the latter branches which form a capillary net- 

 work within the tissue. 



