ACTION OF DUUGS ON CELL LIFE. 229 



tlie health is weak ; and when this is tlie case with one organ 

 alone, we say that it is specially weak. 



Effect of Drugs. — The nutrition of a cell may not only be 

 altered by changes in its supplies of nutriment and oxygen, but 

 it may be modified or destroyed by the addition of certain sub- 

 stances to the nutrient fluid. Thus a weak solution of alkali 

 may increase or diminish the rapidity of the changes which it 

 undergoes, by hastening the removal of waste products if they 

 be acid, or retarding it if they be alkaline ; while a weak acid 

 Avill have an opposite effect. Certain metallic salts may stop 

 them altogether by forming a firm compound with the substance 

 of the cell, while other bodies may enter into combination with 

 it for a time (possibly replacing some ordinary ingredient of its 

 nutriment), again passing out and leaving it in its primitive con- 

 dition, but altering during their stay its physical characters and 

 functional properties. Such seems to be the case with curare, 

 which, when injected into the blood, paralyses the peripheral 

 ends of motor nerves; but, if life be preserved by artificial 

 respiration, the poison is excreted, and its effect passes off* No 

 change can be noticed in the nerve-fibres, either by the naked 

 eye or microscopically, during the paralysis ; and this was sup- 

 posed to show that great functional alterations may occur with- 

 out any structural change. But this is not the case ; for Kiihnef 

 has ascertained that, when the ends of motor nerves in muscles 

 are examined microscopically, their outline is found to be more 

 distinct during the action of the poison. It is possible that the 

 change in physical properties shown by this distinctness of out- 

 line may be only the indication of some more important altera- 

 tion in their chemical composition ; but, v.-hether it be more 

 chemical or physical, a change at any rate takes place ; and to 

 this, I believe, we must attribute the alteration in function. 



Whatever be the composition of protoplasm, the substances 

 which are associated with it in the composition of different cells 

 are at any rate different ; and, although the same nutritive fluid 

 is supplied to them, they do not all take out from it, or give out 

 to iu the same substances in the same proportions, but some take 



* Brodie, Phil. Tram., 1812, p. 205. 



t bti'icker's Histology, Power's translation, vol. i, p. 221. 



