THE SPLEEN AS AN ENDOCRIN ORGAN 667 



of the patient so that the results of splenectomy are not necessarily 

 attributable to a relation of the organ to metabolism. 



The Spleen and Hematopoiesis 



The Spleen and the Lymph Nodes. Hewson seems to have been the 



first to note the anatomic relationship of the spleen to other organs. Since 

 his time numerous investigations have been made, mainly on the lymph 

 nodes, hemolymph nodes, thymus, bone-marrow, and white cells, following 

 splenectomy. The enormous amount of literature which has accumulated 

 on the effect of splenectomy on the lymph nodes has been reviewed by 

 Warthin, Meyer, Pearce, Krumbhaar and Frazier. The results reported 

 are rather conflicting. It can be stated positively, however, that removal 

 of the spleen occasionally produces definite changes in the lymph nodes. 

 Early changes appear to be a hyperplasia of the endothelial cells associated 

 with an increased phagocytosis of these cells for red blood cells. Later 

 the endothelial cells become loaded with blood pigment, and the gland has a 

 reddened or brownish color. 'In my experiments, gross changes in the 

 lymph nodes have been noted only occasionally, but when they have 

 occurred they were quite marked. 



The effect of splenectomy on hemolymph nodes has been reported by 

 Warthin, and their occurrence and distribution have been investigated by 

 Meyer. Warthin studied the hemolymph nodes at various lengths of time 

 after removal of the spleen in goats and sheep and noted the occurrence 

 of a definite hyperplasia. We have examined the hemolymph nodes in 

 six goats after splenectomy at periods varying from nine to four hundred 

 and ninety days. Five of the animals were three weeks old, and one was 

 very old at the time of operation. Only two showed enlargement and 

 hyperplasia of the nodes; in one the changes were very marked. We 

 have not observed hemolymph nodes in the other species of animals such 

 as the dog, cat, rabbit and guinea pig, which we have splenectomized. 



The Spleen and the Thymus. The thymus and spleen have been con- 

 sidered closely related functionally. I have previously reviewed the 

 literature and studied the effect of splenectomy on the thymus in dogs, 

 cats, rabbits, and goats. In general my results were entirely negative. 

 Luckhardt also reports negative results in the rat. The effect of splen- 

 ectomy on the leukogenic activity of the bone marrow and on the white 

 cells will be discussed with more closely related subjects. 



From a review of the mass of data in the literature and from the 

 results of our own studies, it can be stated that splenectomy occasionally 

 produces quite definite, and sometimes marked, changes in the lymphoid 

 structures. These changes seem to be compensatory. They do not appear 

 to be dependent on an internal secretion of the spleen, but rather on the 



