NARCOTICS AND ANODYNES 71 



mental faculties with the external world by bringing about 

 cerebral depression. This disturbing effect is produced by 

 full doses of such agents as alcohol, ether, and chloroform, 

 as well as by most of the agents described as hypnotics. 

 After a variable amount of excitement, locomotor inco- 

 ordination ensues, and the animal staggers in its gait. Then 

 there is drowsiness, stupor, and, with the full action of the 

 drug, coma. Where the effect is still further developed, 

 fatal paralysis of the respiratory centre occurs. The 

 action of these agents is best explained, although not 

 completely, by the theory suggested by Meyer and 

 Overton. These observers have pointed out that the 

 narcotic agents such as chloral, chloroform, ether, and those 

 of the fatty carbon series are alike in being readily soluble 

 in fats and oils, and not so easily soluble, or even insoluble 

 in water. Nervous tissue is largely made up of the fatty 

 compounds cholesterin and lecithin, and as a consequence 

 these narcotic substances circulating in the blood tend to 

 leave this watery fluid and become concentrated in the fatty 

 substances of the nervous tissues. This alters, and in fact 

 lessens, the activity of the nerve-cells, and so accounts for 

 the narcotic or even anaesthetic effect. This theory does 

 not fully explain the action of these drugs, nor is it true of 

 every agent, but, generally speaking, the more soluble in 

 fat and insoluble in water a drug of this series is, the more 

 powerful is its narcotic or anaesthetic action. 



ANODYNES or analgesics are agents which relieve pain by 

 diminishing excitability of nerves or nerve-centres. Pain 

 may originate in the hippocampal region, which Terrier 

 regards as the central seat of sensation, and some abnormal 

 excitement of these nerve ganglia is believed to occur in 

 hysteria. It may depend upon stimulation of the grey 

 matter of the cord, through which painful impressions are 

 conveyed. It may begin in the trunk of a nerve, but fre- 

 quently its origin is in the peripheral endings of the sensory 

 nerves. 



Pain, thus produced in various ways, requires diverse 

 treatment. Its cause should, if possible, be discovered and 

 removed. When merely local, it is combated by local 

 anodynes, such as belladonna, with its alkaloid ; by cocaine, 



