LOCALISATION OF ACTION. 241 



believe tlmt we may by-and-by make tlie substances wliich 

 will produce the physiological effects which we desire, and that 

 a future hes before therapeutics of Avhich at present we can 

 hardly dream. 



II. — Action of Drugs on Protoplasm: General Directions 

 FOR Experimental Investigation. 



British Medical Journal, 1871, Mny 13th, p. 435, and May 20lli, p. 521. 



Modes of Fxperimenting, — Caution. — Action of Drugs on Protoplasm. — Action 

 on Tibriones and Bacteria. — Contagium Vivum. — Action on Fungi; on 

 Fermentation; on Putrefaction; on Oxidation; on White Blood Cor- 

 puscles; on Inflammation. — Action of Gases.— Steps of an Investigation. — 

 Administration of Drugs. — Observation of Effects. — Interpretation of 

 Results. — Minimum Fatal Dose. — Various Channels of Admiuistration. — 

 Excretion. — Mode of Securing Animals. — Instruments reqviired.— Mode of 

 making Cannulae, T-tubes, and Pens.— Narcotising Animals. — Action of 

 Niircotics. — Introduction of Cannulae into Vessels — Injection of Fluids. — 

 IHvision and Irritation of Nerves. — Artificial Respiration; in Mammals; 

 in Frogs. — Admiuistration of Gases or Vapours. 



Gextlemkn, — In experimenting on tlie efTect of drugs, our great 

 object must be to localise their action — to be able to say with 

 certainty, This is the organ on which this medicine acts, and 

 such and such is the action which it exerts upon it. There are 

 two ways in which this might be done. 



1. We might give the medicine to animals of all kinds, from 

 those consisting of one simple cell upwards to the highest 

 forms of life, and mark how its action became modified as we 

 advanced farther and farther from the simple mass of sarcode, 

 and organ after organ became differentiated and developed. 

 Unfortunately, however, the knowledge of comparative anatomy 

 and physiology which is required to interpret the effects that 

 we might thus obtain is so great, and possessed by so few, that 

 this method is at present of little use. 



2. We might take a highly organised animal, not very unlike 

 man in its general structure, and, by operative procedures, allow 

 the medicine to act now on one and now on another part of the 

 body, but never on all at once, till we find out those parts for 

 which it has a particular affinity. 



This scfcond method is the one which we chiefly employ, but 



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