312 ABSOEPTION. 



sistence of the liver, presenting a hilum where the larger blood-vessels enter and the 

 efferent vessels emerge, and covered, except at the hilum, with rather a delicate mem- 

 brane, composed of inelastic, with a few elastic fibres. Their exterior is somewhat tu- 

 berculated, from the projections of the follicles just beneath the investing membrane. 

 The interior of the glands is soft and pulpy. It presents a coarsely-granular cortical 

 substance, of a reddish-white or gray color, which is from one-sixth to one-fourth of an 

 inch in thickness in the largest glands. The medullary portion, which comes to the sur- 

 face at the hilum, is lighter colored and coarser than the cortical substance. Through- 

 out the gland, are found delicate fasciculi of fibrous tissue connected with the investing 

 membrane, which serve as a fibrous skeleton for the gland and divide its substance into 

 little alveoli. The structure is far more delicate in the cortical than in the medullary 

 portion. 



Within the alveoli, are irregularly-oval, closed follicles, about ^-^ of an inch in di- 

 ameter, filled with a fluid and with cells like those contained in the solitary glands of the 

 intestines and the patches of Peyer. These follicles do not seem to occupy the medul- 

 lary portion of the glands, which, according to Kolliker, is composed chiefly of a net- 

 work of lymphatic capillaries, mixed with rather coarse bands of fibrous tissue. The 

 follicular structures in the lymphatic glands resemble the closed follicles in the mucous 

 membrane of the intestinal canal and the Malpighian bodies of the spleen. 



The elaborate researches of Sappey leave scarcely any doubt as to the course and ar- 

 rangement of the lymphatic vessels in the interior of the lymphatic glands, although the 

 view advanced by him that these bodies consist mainly of lymphatics with a little 

 fibrous tissue cannot be sustained. By pricking a perfectly healthy gland with the deli- 

 cate point of his apparatus for injecting the lymphatics, he has seen the mercury succes- 

 sively fill the different capillary vessels and pass into the vasa efferentia. Sappey does 

 not appear, however, to have caused the injection to pass from the afferent to the effer- 

 ent vessels, entirely through this plexus ; and, while the fact of the continuity of these 

 vessels through a capillary plexus is extremely probable, it has not, as yet, been posi- 

 tively proven. 



As far as has been ascertained, the following is the course of the lymphatic vessels 

 through the glands : From two to six vasa afferentia approach the gland, and, when 

 within about a quarter of an inch of it, they break up into numerous small branches which 

 penetrate its investing membrane. In the substance of the gland, these vessels are dis- 

 tributed in the capillary plexus just described and emerge by the vasa efferentia, which 

 are always larger than the afferent vessels and are from one to three in number. In 

 attempting to pass injections entirely through the glands, the fluid has frequently been 

 observed to pass into the small veins ; so that some anatomists have assumed that there 

 is a connection in the substance of the glands between the lymphatics and the blood- 

 vessels. It is altogether probable that the passage of fluids into the veins under these 

 circumstances is due to rupture of the vessels ; and, at all events, the direct connection 

 between them and the lymphatics has never been satisfactorily demonstrated. 



The lymphatic glands are supplied with blood by sometimes one, but generally by sev- 

 eral small arteries, which penetrate at the hilum. These vessels pass directly to the medul- 

 lary portion and there break up into several coarse branches, to be distributed to the 

 cortical substance, where they ramify in an exceedingly delicate capillary net-work, with 

 rather wide meshes, in the closed follicles found in this portion of the gland. This capil- 

 lary plexus also receives branches from small arterial twigs which penetrate the capsule 

 of the gland at different points. Returning on themselves in loops, the vessels unite to 

 form one or more large veins, which generally emerge at the hilum. 



Very little is known regarding the distribution of nerves in the lymphatic glands. 

 A few filaments from the sympathetic system enter with the arteries, but they have 

 never been traced to their final distribution. The entrance of filaments from the cerebro- 

 spinal system has never been demonstrated. 



