9 6 PHYSICAL CHEMISTRY IN MEDICINE. 



Numerous instances in pharmacology, in which any 

 alcoholic radicle in an ester-like combination with an acid 

 is required to bring about any specific effect, can, I be- 

 lieve, be explained in the same way. The alcohol radicle 

 only renders possible the ready absorption of the substance 

 by the cell; the anion connected with it is the really 

 active principle. Cocaine is, for example, a methyl ester 

 of benzoylecgonin, a substituted tropincarbonic acid. 

 The benzoylecgonin, the real carrier of the medicinal 

 properties, is however twenty times less poisonous than 

 its ester, cocaine, and does not possess the anaesthetic 

 properties of the latter. Only after being converted into 

 an ester, through any alcohol whatsoever, is the cocaine 

 effect produced. Existence in the form of an ester is 

 apparently always the sine qua non of a useful local 

 anesthetic whose active anion must 1 enter the endings of 

 the sensory nerves. EINHORN has found that a large 

 number of cyclic and heterocyclic esters are able to bring 

 about a local anaesthesia, and has been able to discover 

 valuable substitutes for cocaine in the orthoforms, which 

 represent methyl esters of amido-oxybenzoic acid, and in 

 nirvanin, a diethylglycocoll compound of orthoform- 

 Eucaine and anaesthesin are also esters, the latter one 

 of p-amido-benzoic acid. Without being directly con- 

 cerned in the physiological effect produced, the presence 

 of an alcohol radicle in the compound first renders such 

 an effect possible, for only under these circumstances is 

 the active acid ion present in sufficient concentration at 

 its point of physiological attack. Arecaidin, which 

 chemically represents a methyltetrahydronicotinic acid, 

 is scarcely active physiologically, while its methyl ester, 

 arecolin, represents the toxic principle of the areca-nut. 



