Studies in Experimental Plethora. 189 



also found that our knowledge of the changes caused by the 

 artificial induction of plethora was in itself meager. 



The effects of repeated transfusions of blood on the blood- 

 destroying and forming apparatus of normal and splenectomized 

 dogs and rabbits have been described. An anemia which devel- 

 oped in two splenectomized dogs during a plethora despite con- 

 tinued blood transfusions has also been studied. 



The decrease or absence of reticulocytes from the blood stream 

 during plethora and their increase during anemia is evidently due 

 to depression and activation of bone marrow activity. The 

 response of the bone marrow is not immediate upon the onset of 

 anemia, but is developed after several days. 



Blood volume studies have served to emphasize the constancy 

 of plasma volume under extreme experimental conditions, and the 

 adaptability of the circulatory system to large increases in total 

 blood volume. 



Blood destruction and elimination as measured by urobilin 

 excretion is greatly increased during the induction of plethora, 

 but still more so during "plethoric anemia." 



Despite intravenous introductions of large quantities of nitro- 

 gen in the form of whole blood, the total nitrogen, urea and 

 ammonia in the urine and feces is not raised appreciably for some 

 time after the onset of plethora. The normal organism is appar- 

 ently able to store large quantities of blood or its decomposition 

 products. Upon the onset of a "plethoric anemia," there is an 

 increase in urinary total nitrogen, urea and ammonia excretion, 

 which is lowered during the course of the anemia. Albuminuria is 

 also found at this time. Other nitrogenous constituents and 

 phosphates show no striking changes. 



Blood pigment, chiefly in the form of hemosiderin, is deposited 

 in enormous quantities in the spleen, liver, lymphnodes and bone 

 marrow. It occurs chiefly in phagocytes, though in late stages 

 large extracellular masses are found. Increased pigment deposi- 

 tion can still be found several months after transfusions have been 

 stopped. 



Phagocytes containing erythrocytes are only occasionally found 

 in the "acute" cases, but their occurrence may have been greatly 

 masked by the coexistent congestion. 



