1868.] Dr. W. H. Broadbent oji the Action of Poisons. 467 



H. Equally striking examples of dislocation of N from C or H cannot 

 be given, and it is not easy in all cases to point out the source of the tension. 

 A very important method in which the balance of affinities is deranged 

 and the condition of tension brought about, is by departure from 

 a stable type, as, for instance, in the nitrite bases, which are residues 

 derived from ammonium-salts by dehydration. To this class belong 

 morphia, strychnia, brucia, and most poisonous alkaloids. Additional 

 interest is given to these compounds by the fact that Dr. Crum Brown 

 and Dr. Fraser have shown that, by introduction into the molecule of 

 methyl-iodide, carrying back the constitution a step in the direction of 

 the ammonium type, the poisonous effects are greatly diminished, and 

 entirely altered in character. 



Let the deduction as to the evolution of nerve-force be accepted, and we 

 have in the introduction into the blood of substances having varying degrees 

 and directions of tension an intelligible method of influencing its mani- 

 festations. 



Looking now upon nerve-action as a result of oxidation, in the various 

 methods by which this oxidation may be influenced, analogies may be 

 traced with conditions which affect ordinary combustion. These condi- 

 tions are — 



1. The supply of oxygen. 



2. The character of the combustible. 



3. The presence of products of combustion, or of bodies having a 

 similar influence. 



It is of course necessary to bear in mind the peculiarities of the oxida- 

 tion yielding nerve-force, the differences between combustion and oxidation 

 in the moist state, and the special modifying conditions of the animal 

 organism. For example, while in asphyxia the deprivation of oxygen 

 arrests all nervous action, the respiration of undiluted oxygen does not 

 intensify it, either because the blood will only take up a certain pro- 

 portion of oxygen, or more probably because the effects of the O are 

 expended in altering the blood, which is thus oxidized instead of being- 

 oxygenated. 



The analogies to the above conditions found in the action of substances 

 on the nervous system are — 



1. The liberation in the nascent state in the nervous structures of C and 

 H, which appropriate the O brought by the blood, and so produce a result 

 equivalent to the exclusion of O. The C and H are set free by the dis- 

 locating influence of N, and the example of this mode of action is furnished 

 by prussic acid. 



The converse of this, the liberation of by a similar process, is not 

 hkely to occur, as is never present in an organic body in excess of 

 the proportion which would fully oxidize the other elementary consti- 

 tuents. 



2. The analogy to the influence on the energy of combustion by the 



TOL. XYI, 2 S 



