80 REACTION OF CELLS 



have entered in reaction with the poison. In this 

 way we may represent to ourselves the manner in 

 which it happens that in every second a certain 

 fraction of the cells is killed by the poison, and that 

 this fraction is independent of the time of action of 

 the poison. 



It may here be worth while to make a little 

 reservation. It is a fact very often observed that 

 immediately after it has been added to the cell- 

 emulsion the poison has a very small action, or 

 none at all. This is easily understood, for it is 

 necessary for the poison to diffuse through the cellular 

 membrane before it is able to act upon the cell. 

 This takes a certain time, which is called the time 

 of incubation. Different bacteria may possess mem- 

 branes which are rather different in regard to their 

 permeability for the poison, and it may also be 

 different for different poisons. It is probably for 

 this cause that the time of incubation is insensible 

 in many of Miss CHICK'S experiments. Only in the 

 case of phenol acting on staphylococci a clear in- 

 dication of the incubation phenomenon may be 

 observed (Fig. 20). But even here the action of 

 the poison is not zero during the four minutes of 

 incubation, but only very small. During this time 

 the cells with the weakest membranes are attacked, 

 and in this manner the small action of the poison is 

 understood. With red blood -corpuscles the said 

 effect is very pronounced, as the experiments of 

 MADSKN and myself indicate. 



