Ill 



A METHOD BY WHICH CELL-DIVISION 

 CAN BE INDUCED IN HUMAN LYM- 

 PHOCYTES IN VITRO WHILE THE 

 CELLS ARE FLOATING IN A SOLUTION 

 WHICH CONTAINS THE NECESSAEY 

 CHEMICAL AGENTS 



By H. C. Ross 



UP to the present, it has only been possible to 

 induce divisions in individual white blood-cor- 

 puscles when the cells are spread out under a 

 cover-glass on the surface of a jelly film set on 

 a slide. The jelly must, of course, contain the 

 proper amount of salts to keep the cells alive, and 

 also an " auxetic " substance which is the immedi- 

 ate cause of the cell-division (1). By this method 

 each cell is pressed into the jelly and has its own 

 portion of jelly surface from which it absorbs the 

 auxetic substance. 



Hitherto, as the cells only appeared to divide 

 in vitro under these conditions, it was thought that 

 they probably had to be resting on a surface before 

 they would undergo mitosis; but, as I shall 

 describe in this note, it has been found that the 

 cells carj. be made to divide while floating in a, 



