466 Dr. W. H. Broadbent on the Action of Poisons. [June 18, 



The force evolved in the animal organism takes the form of heat, motion, 

 and nervous action ; but there are very important points of difference be- 

 tween heat on the one hand and nervo-muscular action on the other, both 

 as to the part they take in the vital processes, and in the conditions of 

 their evolution. 



It is through their action on the nervous system that the powerfuL 

 organic poisons destroy life ; and in order to understand this action, it is 

 necessary to consider closely the evolution of nerve-force, and to endeavour 

 to realize the chemical conditions implied. 



In the first place, the source of nerve-force is oxidation, and the seat of 

 the oxidation is the nervous structures. This is generally admitted, and 

 seems to be conclusively established by an analysis of the phenomena 

 observed in experiments with a prepared frog's leg. 



This admitted, it is to be noted — 



1. That nerve-action is intermittent and of varying intensity, and that 

 in addition to the presence of the oxygen brought to the nerve- structures 

 by the blood, an impulse from without, or from some other part of the 

 nervous system, is necessary to determine the evolution of the force. 



2. Again, there is a storing up of potential energy in the nervous struc- 

 tures ; witness the necessity for sleep, &c. 



3. A due supply of oxygen is required. The phenomena of asphyxia 

 show that the demand is most urgent in the hemispherical ganglia. 



These facts indicate that the constituent of the nervous structures by 

 oxidation of which the force is yielded, possesses what I have ventured to 

 call chemical tension, a property which does not belong to non-nitrogen- 

 ized matter, or to all nitrogenized matter. It will be further explained 

 later ; for the present, it is sufficient to refer to nitroglycerine as an ex- 

 treme example. 



The protagon of Liebreich, and the neuriue recently identified by Wurtz, 

 with hydrate of trimethyl-oxethyl-ammonium, have this characteristic in 

 a certain degree. 



Turning now to the poisons which kill by their powerful action on the 

 nervous system. They all contain nitrogen, and all possess chemical ten- 

 sion ; and these seem to be the only points common to the entire group. 



Nitrogen cannot be the poisonous element ; it has no great chemical 

 energy, and it is present in large proportion in substances which are 

 inert. It is nevertheless the pivot on which the deadly influence turns. 

 Its affinity for H, O, and es])ecially for C, is only feeble. When, therefore, 

 in a molecule containing C, H, and N, or C, H, N and O, the elements are 

 not so arranged that the mutual affinities of C, H, and cooperate to 

 maintain the integrity of the molecule ; there may be a more or less powerful 

 tendency on the part of C, H, and O to rearrauoje themselves without re- 

 gard to the N, or to combine with O or II^ O if presented. This is what 

 is meant by the term chemical tension. In the example given, nitrogly- 

 cerine { 031X5(^^02)30 J, the dislocation is of from N in favour of C and 



