INFLUENCE OF POISONS ON PHCVroi'LASM, ETC. HARRIS. 99 



sufTocation. Comprisinfi; the vitality of the tissues l)y 

 chemical means, is inherent in the notion of a poison. Any 

 chemical substance which interferes witli the action of the 

 heart or of the respiratory centre to such an extent as to im- 

 peril life is a poison. Unquestionably certain drugs are in- 

 cluded under this heading. Here we are not thinking of such 

 things as crude acid or alkali which has been swallowed and 

 has destroyed the very tissues themselves; these indeed com- 

 promise life and are therefore poisons. Nor are we thinking 

 of such a substance as strychnine which kills in a round-about 

 way by asphyxia. It causes such prolonged inspiratory 

 spasms of the diaphragm that breathing is interfered with 

 and the due entrance of oxygen into the blood and thence 

 to the tissues effectually prevented. 



In a sen.se, strychnine kills as mechanically as does a 

 rope tied round the neck; both ultimately prevent the access 

 of oxygen to the living tissues. It is the narcotic poisons 

 which present the tj^pical problem to the physiological 

 chemist. 



Why and how^ are alcohol, chloroform, ether, morphia, 

 cocaine, and hydrocyanic acid poisons? On what preciseh' 

 do the}' act; and is that thing the same substance as that on 

 which perchloride of mercury, for instance, exerts its bane- 

 ful influence? 



Do poisons act on protoplasm or on the i)roducts of 

 protoplasmic activity, such as the enzymes? For it is prac- 

 tically certain that a poison must either compromise the pro- 

 per functional activity of the biogens or living molecules, 

 or it must interfere with the due action of some one or more 

 of the enzymes possessed by or liberated b}^ the protoplasm. 

 Thus for convenience we speak of a protoplasmic poison which 

 kills living protoplasm, and of an enzymic poison which 

 prevents its fermentative activity. 



Pro. & Trans. N. S. Inst. Sci. Vol. XIV. 21 Jl 16. Trans. 7 



