176 MANUAL OF HISTOLOGY. 



distribution does not concern us here ; it is sufficient to say 

 that they are very variable in size and number in different 

 regions, being supplied to nearly all the lymphatic trunks, 

 with which they are connected by the so-called afferent and 

 efferent branches. The former usually consist of several small 

 branches ; the latter generally enter as single large trunks. 



The shape of the lymph-nodes may be spherical, oval, ob- 

 long, or reniform. In the latter, which is by far the most fre- 

 quent form, the afferent vessels penetrate the capsule on the 

 convex surface, while the efferent branch escapes at the hilus. 

 In the other forms it is difficult to determine which are the 

 afferent and which the efferent vessels. A lymph-node con- 

 sists essentially of spheroidal and cylindrical masses of reticular 

 tissue, containing lymphoid corpuscles, richly supplied by a 

 blood-capillary system, and sustained in place by a framework 

 of connective tissue, with elastic and sometimes muscular ele- 

 ments, forming a network around the masses for the circula- 

 tion of lymph, and expanding externally to form a capsule. 

 The gland is usually divided by histologists into a cortical and 

 a medullary portion, the former being simply that part in which 

 the lymphoid masses assume a spheroidal form (the follicles), 

 this being the more peripheral portion of the node, or the part 

 farthest from the hilus, when that exists. The medullary sub- 

 division represents the remaining portion, and its lymphoid 

 material is in the form of cylindrical or cord-like prolongations 

 from the follicles. The capsule is composed of connective tis- 

 sue, the fibres of which run in different directions in its exter- 

 nal layers, possessing elastic fibres, flat cells, and a slight 

 amount of fat-tissue. The lymphatics of the capsule are found 

 mostly in its outer layers. The inner layers present a more 

 stratified appearance on account of the regularity of their 

 bundles and the interposed connective-tissue cells. An elastic 

 network and smooth muscular elements are found here, and 

 nlso in the septa, and are developed in some animals to a high 

 degree. It is from the inner layers of the capsule that the 

 septa are given off to form the framework of the node. These 

 consist primarily of trabeculse, which, passing between the fol- 

 licles, converge toward the medullary portion, where they inter- 

 lace with the lymphoid cords of the latter, and may again unite 

 at the hilus (stroma of His). They have a structure similar to 

 that found in the portion of the capsule from which they have 



