Hypersensitiveness to Horse Serum. 



The lung lesions described by Gay and Southard in the acute cases 

 are here very slight. The gastric necroses are often very exten- 

 sive. There are frequently large hemorrhagic necroses in the 

 spleen. The mesenteric lymph nodes show desquamation of the 

 endothelial cells of the sinuses. There are some red blood cor- 

 puscles in the sinuses. The endothelial cells are in various stages 

 of degeneration, show some evidence of having acted as phagocytes, 

 and the red blood cells are agglutinated around them in rosette- 

 like arrangement. (Demonstration.) 



In the spleen bordering the necrotic areas there is very marked 

 phagocytosis of red blood corpuscles by large mononuclear cells. 

 As contrasted with other instances of phagocytosis of erythrocytes 

 this case has the following features. Usually but one corpuscle 

 is found within the phagocyte. The enclosed corpuscle at first 

 swells and has an increased affinity for eosin. Then the color 

 reaction fades out and the corpuscle remains as a shadow which 

 becomes smaller. Pigment is not common within these phagocytic 

 cells. This form of phagocytosis with intracellular lysis is not a 

 peculiarity of the guinea pig. In other conditions in this animal 

 one finds phagocytic cells filled with numbers of rather shrunken 

 deeply bronzed erythrocytes or with pigment particles evidently 

 of erythrocytic origin. Comparison of the two classes of cases 

 indicates, either that intracellular blood destruction in cells of 

 endothelial type may be accomplished in ways that are funda- 

 mentally distinct, or that the factors of dissolution of the erythro- 

 cyte and segregation of the pigment constituents are independent 

 and may run at different rates. 



Recurring to the picture in the mesenteric lymph nodes, it 

 seems possible that the endothelial cells may be the source of 

 origin of certain serum hemagglutinins. It is an obvious sug- 

 gestion also that agglutination functionally considered may be a 

 constant factor in phagocytosis, serving to bring the subject cell, 

 in this instance the erythrocyte, in contact with the phagocyte, in 

 this case the endothelial cell. 



This sharp reaction of the subcutaneous tissues resulting fre- 

 quently in necrosis is closely analogous to the reaction which 

 Arthus obtained to repeated subcutaneous doses of horse serum in 

 the rabbit. It seems probable that it is a protecting factor so far 

 as the animal is concerned. 



