THE CYLE OF CELL-DIVISIOX 



cell-reproduction, and in vitro the only way to cause 

 it to take place was to force the cells to absorb the 

 chemical "exciter of reproduction" contained in the 

 aniline dye. It appeared reasonable to us to suppose 

 that there might be other "exciters of reproduction," 

 not only for lymphocytes, but for other cells as well, 

 and therefore we proposed to call the substance in the 

 aniline dye which caused cell-division in lymphocytes 

 an "auxetic" (dwfjjrwos, an exciter of reproduction), 

 a convenient term suggested by Professor Harvey 

 Gibson, which might be applied to other substances 

 having a similar action if such were proved to exist. 



The next steps were to investigate the "augment- 

 ing" actions of both atropine and the extract of haemal 

 gland. It has been pointed out how atropine, being 

 an alkaloid, greatly excites amoeboid movements in 

 lymphocytes and leucocytes, and it was soon seen that 

 atropine also greatly augments the action of the poly- 

 chrome dye in inducing mitotic figures in lymphocytes. 

 The best strength of atropine to be added to the jelly 

 which contains the stain is that which causes maximum 

 excitation of amoeboid movements. If this is done 

 lymphocytes can be caused to divide with the strength 

 of the stain reduced to one-fifth of the minimum 

 amount of it which will, by itself, induce mitotic 

 ^figures. In other words, atropine will not by itself 

 induce divisions on the microscope slide, but it will 

 augment the "reproducing" action of polychrome stain 

 five-fold. Another point was also noticed, which was 

 very material to the main object of these researches, 

 in that stain, plus atropine, caused lymphocytes to 



