46 CHEMICAL AGENTS AND PROTOPLASM [Cn. I 



All the reagents with which we have dealt have been sub- 

 stances capable of absorption by, mixture with, or solution 

 in, water ; and the reason for this is that almost all proto- 

 plasm is itself enveloped by water and largely composed of 

 water. 



For the most part we have dealt with mixtures or solutions. 

 Now the action of these is a double one. They exhibit, first, 

 an osmotic action, and, secondly, they may attack the molecules 

 of the protoplasm, transforming them. The osmotic action we 

 will consider in the third chapter ; the transforming one alone 

 concerns us now. It is not easy, without experiment, to say 

 to which of these two categories of action the change wrought 

 by any substance is due. To determine between the two 

 possible causes it would be desirable in each case to treat the 

 protoplasm to a control solution having the same osmotic action 

 as the first, but no transforming effect. If such a solution 

 produces no modification of the protoplasm, then the effect 

 wrought by the first reagent is due purely to molecular trans- 

 formations. It is not easy to find a reagent of which we may 

 be certain that it acts only osmotically. NaCl is probably more 

 generally useful in this way than any other substance. In the 

 experiments which have hitherto been made, this double action 

 of solutions has not been sufficiently considered. Hence, a 

 doubt concerning the immediate cause hangs about many of 

 the phenomena described in the first section. 



The first principle which the data collected establish is 

 that the protoplasm of different organisms is dissimilar. This 

 is shown by the diversity in their chemical reactions ; by the 

 fact that whereas, in one case, a certain percent solution 

 causes so extensive a molecular transformation as to result in 

 death, in another, no injurious effect is produced. 



Thus, according to BOER ('90, p. 479), it takes of gold 

 chloride to kill 



TABLE V 



Anthrax bacillus 0.0125% 



Cholera spirillum 0.1% 



Diphtheria bacillus 0.1% 



Typhoid bacillus 0.2% 



Glanders bacillus 0.25% 



