No. 2.] CHANGES IN THE SPLEEN OF THE FROG. 407 



Rana Temporaria. 





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companiecl by an increase in the number of "nurse" cells. 

 The same is true of the esculenta spleens in summer, whereas 

 in winter the elevations of the "nurse" cell curves nearly 

 correspond to the elevations of the size curves. The compari- 

 son of Figs, b and c seems to teach that the spleens containing 

 a small quantity of blood are richer in "nurse" cells than 

 spleens containing a large portion of blood. In comparing 

 Figs, c and e we find that 

 the elevations of eosinophilous 

 cell curves in November coin- 

 cide with the elevation of the 

 "nurse" cell curve for the 

 same month. The May and 

 June elevations of the "nurse" 

 cell curves precede the June 

 and July elevations of the 

 eosinophilous cell curves. The 

 elevations of the follicle cell 

 curves (Figs, d and e) suc- 

 ceed those of the "nurse" 

 cell curves, thus coinciding, in 

 part, with the eosinophilous 

 cell elevations, as was noticed 

 above. If we recall the facts 

 concerning the "nurse" cells 

 given in Gaule's Strassburg 

 lecture and his opinion that the " nurse " cells are devel- 

 oped from the other white blood corpuscles, it no longer 

 estranges to find that the proportion of these elements varies 

 among themselves at a time when the tide of blood in the 

 spleen is at its ebb. 



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Fio;. e. — "Nurse "-Cell Curves. 



f. Cytosoa Curves. 



The general conclusion to be drawn from these curves is 

 that the cytozoa are more frequent soon after the month 

 of copulation and after the close of the food period. They are 

 more numerous in the esculenta than in the temporaria spleens. 



