172 THE ORGANS 



blends with the surrounding tissuesk3,nd serves, hke the fibres of the 

 arterial adventitia, to attach the organ to them. ^The inner layer 

 of the capsule consists of a more dense connective tissue, is richer in 

 elastic fibres, and contains some smooth muscle cells. At one point, 

 known as the // Hum (Fig. 99), there is a depression where the con- 

 nective tissue of the capsule extends deep into the substance of the 

 node. This serves as the point of entrance for the main arteries 

 and nerves, and of exit jp_r_the veiiis and efferent lymph vessels.:; 



It g f 



Fig. 99. — Section through Entire Human Lymph Node, including Hilum. X15 

 (Technic i,p. 176.) Dark zone, cortex; light central area, medulla, a, Lymph nodule 

 of cortex; b, germinal centres; c, trabeculae containing blood-vessels; d, capsule; e, 

 hilum; /, lymph sinus of medulla; g, lymph cords of medulla; It, lymph sinuses of 

 medulla and cortex. 



The connective-tissue septa, which extend from the capsule into 

 the interior of the node incompletely divide it into irregular inter- 

 communicating compartments. In the peripheral portion of the 

 node these compartments are somewhat spheroidal or pear-shaped. 

 Toward the centre of the node the septa branch and anastomose 

 freely, with the result that the compartments are here narrower, 

 more irregular, and less well defined. 



Within the compartments formed by the capsule and the septa is 

 the lymphatic tissue. Near the capsule where the compartments 

 are large and spheroidal or pear-shaped, the lymphatic tissue is 

 arranged in masses which correspond in shape to the compartments. 



