86 A. P. Mathews 



bility in which saUs affect the protoplasmic movements in virtue of 

 their own energy content. 



In this case also the action of the salt may be twofold. It may 

 either change the whole protoplasmic system by means of the energy 

 in the salt, or it may by a transfer of a portion of its energy to one part 

 of the protoplasm produce such a change in the latter that energy is 

 set free by the protoplasm itself. It is clear, in other words, that the 

 salt may destroy the protoplasm either directly, in virtue of a great 

 interchange of energy between itself and the protoplasm, or it may 

 destroy it indirectly, by acting on some part of the protoplasm in 

 such a way that its own energy destroys it, or that the normal con- 

 version of potential into kinetic energy necessary for the continuance 

 of the vital processes is checked. 



A distinction is generally made between these two forms of destruc- 

 tion, in that substances acting in the first manner are said to be imme- 

 diately fatal; those acting in the second manner are said to exhaust 

 the protoplasm by over-stimulation or depression. Thus mercuric 

 chloride in large doses probably produces an immediate coagulation 

 and destruction of the living matter. In this case an immediate and 

 complete change in the protoplasmic system would be produced by 

 the transfer of energy from the salt to the protoplasm as a whole. On 

 the other hand, mercuric chloride may destroy living matter in small 

 doses, not by this method, but by bringing about a small change in 

 the protoplasm, by means of which internal resistance of some kind 

 is withdrawn or increased, and the protoplasm destroys itself. In 

 both these cases, however, the destruction of the protoplasm is a 

 direct result of the energy content of the salt, and salts will be poison- 

 ous according as the amount of free energy in them is great or small. 



For all salts and compounds producing changes in the proto- 

 plasmic system in the two last ways the chemical composition will 

 be of little or no importance ; the sole or most important factor deter- 

 mining action will be the potential and amount of the energy in it. 

 The character of the carrier of the energy, in other words, is imma- 

 terial. 



The foregoing considerations may be expressed in a formula : 



Poisonous action of any sali—work done by it = avail- 

 able energy in it = amount of energy X its potential. 



