132 THE EXCITATION OF AMCEBOID MOVEMENTS 



not so treated. The poison was mixed up with the 

 stained jelly, and that jelly was alkaline, in order to 

 cause the diffusion of the stain and of the poison into 

 the cells. The poison chosen in the first instance was 

 hydrocyanic acid, and then nitrobenzol was used; but 

 after subjection to them, the cells presented very little 

 difference from others not so treated and known to be 

 alive. At last atropine sulphate was tried, with a very 

 astonishing and unexpected result, for every leucocyte, 

 far from being killed outright, became excited to great 

 activity. Some time afterwards it was realised that 







this excitation by atropine was very constant, and that 

 if a cell was placed on a suitable jelly which contained 

 atropine, it w T ould, if alive, respond with absolute 

 certainty by exhibiting excited amoeboid movements. 

 Thus the means of measuring the lives of leucocytes 

 was determined, and it became a simple matter, by 

 examining the leucocytes in a given sample of blood- 

 over a series of intervals to discover how long they 

 lived under varying conditions, for one was enabled 

 at once to say whether the leucocytes were living or 

 dead, the living ones showing exaggerated movements, 

 the dead ones remaining immobile. 



This method of measuring the lives of leucocytes, 

 and the details connected with it, will be found in the 

 Appendix. It was originally intended to use it for 

 ascertaining the effect of toxins on leucocytes, and we 

 think that for this it will have a useful application. 

 Owing to the fact that the excitation by the alkaloid 

 led to other work, we have not yet had time to in- 

 vestigate the actions of toxins very far. 



