156 PHYSIOLOGY. 



Lymphatic Glands. 



Lymphatic glands are shaped much like a kidney. The oblique 

 afferent vessels approach their convex border, whereas the efferent 

 vessels, which are larger and more numerous, escape from the hilum 

 on their concave border. Their consistence is that of the liver, and 

 'their color varies in different regions, but usually is a rosy white. 

 In size they vary from an olive to those invisible to the naked eye. 

 As age advances, the glands become much smaller. Their number 

 is 600 to 700. The glands are almost always buried in a bed of 

 adipose connective tissue, usually united in groups of three to six, 

 or even ten to fifteen, forming chains or chaplets. Their situation 

 is generally paravascular and paraepithelial. A lymphatic gland 

 consists of three parts: (1) the capsule, (2) the cortex, and (3) the 

 medulla. The cortex is composed of a number of cells, the majority 

 of which are small. The nucleus is rounded or quadrangular, and 

 has a thick chromatin border; in its center are one or two chromatin 

 granules. Sometimes, but not always, a true nucleolus is found. 

 These elements are identical with the microcytes of blood and lymph 

 (lymphocytes). The large cells correspond to macrocytes. The 

 follicles of the cortex formed by the trabecula of connective tissue 

 have no proper wall; they are limited by the endothelium of the 

 lymphatic sinus, which surrounds them. The follicle with the clear 

 center is essentially a seat of cellular reproduction, and it has been 

 termed a germinitival center, a seat of karyokinesis. 



The Medulla. The medulla presents cords, irregular in size, 

 shape, and course. These cords anastomose with each other and are 

 separated from each other by large, clear spaces, the cavernous 

 sinuses. The medullary cords are central prolongations from the 

 cortex, and are formed of the same cells, which are here sometimes 

 agglomerated. Between the cords the cavernous sinuses show us 

 the best place for studying phagocytosis of the gland and of the 

 reticulum. The reticulum is formed by an anastomosis of cellular 

 prolongations. Some of the cells of the reticulum have an elon- 

 gated, clear nucleus; others have distinct nuclei. 



Afferent Vessels of the Lymphatic Gland. The afferent lym- 

 phatics pass through the capsule, lose their tunica adventitia and 

 muscular coat, and, like true capillaries, become reduced to their 

 endothelium. By the anastomosis of their capillaries they form a 

 vast peripheral sinus, which generally separates the capsule from 

 the follicles. From the sinus, interfollicular branches, which reach 



