2OO THE BLOOD AND BLOOD-FORMING ORGANS. 



not only the lymph-nodules of the cortical substance, but also the 

 medullary cords, and finally streams into the terminal sinus and 

 then into the efferent channels. As a result the lymph takes with 

 it the newly formed cells of the lymph -nodules and the medullary 

 cords, and passes out richer in cellular elements than on its entrance. 



The lymph-glands receive their blood supply mainly through 

 the hilum ; relatively small arterial branches may penetrate the 

 capsule. Generally, a number of arterial branches enter at the 

 hilum, from whence they may pass directly into the medullary 

 substance, or pass for a distance in trabeculae. In their course 

 branches are given off which pass to the medullary cords, in which 

 they break up into capillary vessels situated in the periphery of the 

 cords. These unite to form small veins which anastomose freely, 

 and unite to form larger veins. The cortical nodules receive their 

 blood supply from arterial branches which enter their proximal 

 sides (side toward the hilum) and course through the center of the 

 nodules, giving off capillary vessels which pass, without much 

 anastomosis, to the periphery of the nodules, where they unite to 

 form plexuses ; the capillaries of these plexuses join to form the 

 veins of the nodules, which are thus situated at their periphery. 

 These veins unite to form larger veins, which leave the glands at 

 the hilum (Calvert). 



Medullated and nonmedullated nerves penetrate the lymph- 

 glands accompanying the blood-vessels on which they terminate. 



Hemolymph Glands. A typical lymph-gland possesses afferent 

 and efferent lymph-vessels and a closed blood-vascular system 

 completely separated from the lymph-vascular system, as may have 

 been seen from the foregoing description. Attention has, however, 

 been called in recent years to certain lymph-glands in which the 

 complete separation of the vascular and lymphatic systems does 

 not obtain, glands in which the formed elements of blood and 

 lymph are intermingled in the meshes of the adenoid reticulum, 

 and which contain blood-sinuses in place of the lymph-sinuses 

 observed in the typical lymph -glands. These have been designated 

 as hemolymph glands (Blutlymphdrusen, hemal glands, hemal 

 lymphatic glands). In the typical hemolymph glands there are 

 no afferent and efferent lymphatic vessels ; the glands are inter- 

 calated in the vascular system. Certain less clearly defined hemo- 

 lymph glands possess afferent and efferent lymphatics and blood- 

 sinuses, the two systems being not completely separated. These 

 may be considered transitional forms. 



Lymph-glands with blood-sinuses were first described by Gibbes, 

 who found such glands in the region of the renal artery. They 

 were further considered and more fully described by Robertson, to 

 whom the term hemolymph glands is to be credited, and by Clark- 

 son, Vincent and Harrison, Drummond, Warthin, Weidenreich 

 and Lewis. It appears from their description that they are widely 

 distributed among vertebrates, although not equally well developed 



