74 The Normal Histology of the Human Hemolymph Glands 



cells, eosinophile, basophile and mast-cells may at times be found also 

 in the reticular meshes. The origin of the phagocytes has not yet been 

 definitely determined; they may arise either from leukocytes or from 

 the endothelial cells lining the reticulum. 



Vascular System. — The exact manner of circulation in these glands 

 has not yet been worked out, but it seems probable that the arteries 

 entering the hilum quickly divide into small branches which, passing 

 toward the periphery, empty into the blood-sinuses from which the 

 blood is again gathered into veins which pass out at the hilum 

 or obliquely through the capsule. As in the lower animals, there are 

 great individual differences in the number and mode of branching of 

 the blood-vessels. Occasionally the entering arteries pass along the 

 trabecule and do not divide until near the periphery. In well-stained 

 sections the course of the blood-sinuses and vessels is well shown by 

 the blood contained in them which serves the purpose of an injection. 

 The exact manner of communication between arterial and venous 

 systems cannot, however, be made out by this means. Injections have 

 not yet been attempted in the human subject, but in the lower animals 

 they have been unsatisfactory. The circulation in the sinuses is of the 

 type known as sinusoidal, only the endothelium separating the blood 

 from the cells contained in the reticular meshes. The current in these 

 spaces must be extremely slow and a long period of time must be 

 required for the complete circulation through the intricate meshes of 

 the reticulum crossing the sinuses. 



In the splenolymph glands containing blood-sinuses throughout, af- 

 ferent and efferent lymph vessels are not found, small lymphatics alone 

 being present in the capsule. In glands of mixed type containing 

 lymph-sinuses lymphatic vessels are also found. Whether there is any 

 communication between the lymphatic and blood-systems in these 

 glands remains yet to be shown. In the round masses of cells lymph- 

 spaces or capillaries are probably present as in the splenic follicles, 

 since under certain pathological conditions these may become edema- 

 tous, the cells being separated by an accumulation of fluid in the inter- 

 cellular spaces. These lymph spaces probably empty directly into the 

 blood-sinuses and convey leukocytes into the circulation. 



Varieties. — As already mentioned transition forms exist between the 

 splenolymph glands and the spleen on one hand and ordinary lymphatic 

 glands on the other. The significance of these intermediate forms is 

 not yet apparent. 



Development. — No work has yet been done on the development of 

 these glands. They are present as fully-developed organs in the new- 



