LYMPH GLANDS 



20 5 



sents a younger stage than the right half. These instructive figures were 

 prepared by Stohr on the basis of Kling's studies (Arch. f. mikr. Anat., 

 1904, vol. 63, pp. 575-610). In the youngest stage (Fig. 194) it is seen 

 that the blood vessels enter and leave the gland on one side, at a place 

 called the hilus (Lat. hilum, a small thing, applied to the eye of a bean, 

 and to similar hollows in bean-shaped organs). The lymphatic vessel, 

 as a plexiform peripheral sinus, encircles the entire structure. After 

 the gland has enlarged, lymphatic vessels extend into the mass of lymphoid 

 tissue, as shown on the right of Fig. 194, and eventually they pass clear 



/ 



- : < Nssss;j r * ( 

 .%^B?V 



FIG. 192. THE FIRST AXILLARY LYMPH GLAND OF FIG. 193. ONE OF THE EARLIEST CERVICAL LYMPH 

 THE RABBIT. FROM AN EMBRYO OF TWENTY GLANDS. FROM A HUMAN EMBRYO OF 42 

 DAYS. 29 MM. X 60. MM. X 60. 



a, Artery; g, lymph gland; 1, lymphatic vessel; v, vein. 



through it in a system of anastomosing sinuses. The lymph then flows 

 into the gland from the periphery, and out at the hilus; both the afferent 

 and efferent vessels are shown in Fig. 195. Finally a connective tissue 

 capsule develops around the larger glands, and in some of them it extends 

 into the interior, producing a system of supporting trabeculcs, either round 

 or lamellar. These may unite with one another as shown on the right of 

 Fig. 195. When present within the gland they are always found in the 

 central axes of the lymph sinuses. 



By the production of the internal lymph sinuses, the substance of the 

 gland is subdivided into rounded nodules and elongated cords of lymphoid 

 tissue. The nodules are found at the periphery of the gland and col- 

 lectively they form its cortex; the cords constitute the medulla. Several 

 other organs, e.g., the kidney and suprarenal glands, are divided into an 

 outer cortex (bark) and an inner medulla (pith). . In the center of each 

 cortical nodule there is often a light spot, seen with low power, which 

 constitutes the germinal center. These general features of a lymph 

 gland are shown in Fig. 196. It is evident that certain of the secondary 



