No. 2.] CHANGES IN THE SPLEEN OF THE FROG. 409 



h. Figures of Cell- Division Curves. 



It is evident from the curves that cell-division in the spleen 

 is confined to a certain period, this occurring in the months of 

 May, June, and July. They are most frequent in the female 

 spleen in June and July; in the male in May and June. 



i. Plasmosonia. 



In general they are more frequent in winter than in sum- 

 mer. The presence of plasmosoma in the nuclei indicates 

 that the nuclei are larger and 

 more distinct in such spleens 

 than in others, and that the 

 structure of the nuclei has 

 assumed a special character. 

 Their curves must be looked 

 upon as merely a preliminary 

 study of the minuter structure 

 of the cells of the spleen. 



Rana Temporaria. 



2 -S d 

 fe S < 



S ^ w) 



"3 



5 /3 



a 2 



< w O I? Q 



k. Protoplasm. 



From my notes I learn that 

 the esciilenta spleen contains 

 a greater proportion of proto- 

 plasm, as compared with the 

 nucleus - substance, than the 

 temporaria spleen ; the male 

 spleens a greater proportion of 

 protoplasm than the female. 

 From July to October the pro- 

 toplasm has a net-like character, as though it contained fat or 

 some fluid in its meshes. The protoplasm of the esculcnta 

 spleen is more nearly homogeneous than the temporaria. 



1 



Fig. g. — Pigment Curves. 



Summary (compare Figures k, /, m, n). 



If we group the curves of the single elements over one 

 another, under the four heads, temporaria $ and 9, esculenta 



