II 



A METHOD OF MAKING PERMANENT 

 EIXED EILMS OE HUMAN LYMPHO- 

 CYTES IN WHICH DIVISION EIGUEES 

 OE OTHER, PHENOMENA HAVE BEEN 

 INDUCED BY CHEMICAL AGENTS 

 WITH THE " JELLY METHOD" 



By J. W. CROPPER and H. C. Ross 

 (By H. C. Ross) 



WITH the jelly method of in-vitro staining (1), the 

 films could not hitherto be kept, because the cells 

 soon died and then became disorganised and 

 disappeared. All attempts to fix the cells in 

 the act of division or of extruding pseudopodia 

 failed, and we had to resort to photomicrography 

 to record the specimens a procedure which was 

 elaborate and unsatisfactory, and, of course, gave 

 pictures not comparable with those presented by the 

 cells themselves. The chief difficulty in fixing 

 the films lay in the fact that one could not remove 

 the cover-glass without disarranging the cells and 

 distorting them. When they are resting between 

 the jelly and the cover-glass they become admirably 

 arranged side by side while they absorb the sub- 

 stance from the jelly, but if the cover-glass is even 

 touched, the living and floating cells all run 



34 



