HEMOLYMPH NODES 239 



mitosis has been most frequently observed in the large mononuclear type, 

 and is most abundant in the germinal centers of the nodules. The 

 small mononuclear and polymorphonuclear types have also been shown to 

 be capable of cell reproduction by indirect division. Eeproduction by 

 direct division of leukocytes appears to be rare, if indeed it ever actually 

 occurs. 



The mononuclear as well as the polymorphonuclear forms appear to 

 be phagocytic. Among the inclusions which have been found within 

 these cells are fat globules, pigment granules, red blood corpuscles in 

 partial disintegration, insoluble pigments, such as carbon granules, etc., 

 and bacteria. The cells of the reticulum are also believed to be phago- 

 cytic. 



Blood-vessels. The arteries enter the lymph node at its hilum, and, 

 following the trabeculae within which they lie, are distributed to all por- 

 tions of the organ. In the medulla branches are distributed to the 

 lymph cords, in which they form a wide-meshed capillary plexus. 



The terminal branches of the primary divisions of the afferent artery 

 are distributed to the nodules of the cortex. A single nodular branch 

 (Calvert, Anat. Anz., 1897) enters the nodule and passes straight toward 

 its center, where it breaks into a plexus of divergent capillaries which 

 unite at the surface of the nodule to form small venous radicals. 



The veins follow the internodular trabeculae in their course toward the 

 medulla, where they enter the medullary trabeculae, are augmented by 

 venous radicals from the capillary plexuses of this portion of the gland, 

 and thence follow the trabeculae to the hilum, where they unite to form 

 the efferent vein. 



Certain of the arteries also pass from the medulla through the inter- 

 nodular trabeculae to the capsule of the gland, to which they supply 

 a capillary plexus. The blood is returned through veins which retrace 

 the course of the arteries and enter the large veins of the medullary 

 trabeculae. The spleen contains no lymphatics beyond the capsule. 



HEMOLYMPH NODES 



(Hemal Nodes) 



These structures, which closely resemble the lymph nodes, were first 

 described by H. Gibbes (Quart. Jour. Mic. Sc.), in 1884. He found 

 them in the connective tissue between the renal artery and vein, in the 

 human subject. They have since been found in the prevertebral connec- 

 tive tissue, and in the mediastinum and mesentery. They are larger and 

 16 



