PLATE 1 



EXPLANATION OF FIGURES 



The outlines were first drawn with the aid of a camera lucida at a magnification 

 of 770 diameters. In the reproducing of the drawings the illustrations were 

 reduced to 575 diameters. The sections from which the drawings were made 

 were 4m thick and stained in hematoxylin and eosin. 



1 Normal spleen of rabbit, showing several splenocytes with inclusions. Spi, 

 splenocyte with single inclusion, colored with blood pigment. Sp%, splenocyte 

 with several vacuole-like areas in its cytoplasm. Spz, splenocyte with inclu- 

 sions of polymorphonuclears. 



2 Spleen of rabbit, six hours after injection of pigeon corpuscles, showing 

 myelocytes in the vascular channels. Sp, splenocyte with inclusion colored with 

 blood pigment. B, extracellular mass of blood pigment. My\, myelocyte show- 

 ing stage of mitotic division, with chromosome-like masses of chromatin. My2, 

 myelocytes with pseudo-eosinophilic granules. 



3 Spleen of rabbit, six hours after injection of pigeon corpuscles, showing 

 myelocytes (My), pseudo-eosinophilic polymorphonuclear leucocytes (P), mega- 

 cyte (M), splenocyte (Sp), and blood pigment, both intracellular and extracellular. 



4 Spleen of rabbit, sixteen hours after injection of pigeon corpuscles, showing 

 three splenocytes with cellular inclusions. N.Sp., nucleus of splenocytes. 



5 Spleen of same rabbit shown in figure 4. Shows a splenocyte greatly en- 

 larged by reason of its numerous cell inclusions. N.Sp., nucleus of splenocyte; 

 R, reticuloendothelial cells. 



6 Spleen of rabbit, forty-eight hours after injection of pigeon corpuscles, 

 showing two splenocytes with inclusions. The splenocytes (Sp) are now becom- 

 ing smaller, as the digestion of the phagocytosed cells approaches the end of the 

 process. 



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