THE RELATIONS OF THERAPEUTICS 163 



Since the time that chloral came into use, organic bodies have been 

 particularly investigated. Owing to the tremendous amount of 

 material, there has been a tendency to place reliance upon the chem- 

 ical composition in making a choice, and it has been assumed that 

 the chemical constitution stands in a certain relation to the action 

 of a drug. Many experiments have been made in this direction. We 

 do not wish to deny that such an influence occasionally exists ; at any 

 rate, we see that when the action of a given substance is known, 

 changes in the molecule will produce a difference in action, and that 

 by the introduction of certain groups certain definite changes in the 

 effect may be expected. Among this group of bodies is antipyrin, in 

 which changes in the side-chains leave the nature of the effect 

 pretty much the same, even though new therapeutic advantages are 

 obtained, as is best seen in pyramidon. A similar example is offered 

 by veronal, lately suggested by E. Fischer as a soporific. 



But it is as yet impossible to predict the effect of a chemical body 

 from its constitution, unless a decomposition product of known 

 action is formed, as in the case of chloral hydrate, or unless an active 

 and well-known nucleus forms the basis of the substance. There are, 

 of course, examples which point to the connection between consti- 

 tution and effect, such as the difference between the action of bi- 

 and trichlorinated aliphatic combinations. The trichlorinated bodies 

 have a lethal influence on the heart; the bichlorinated bodies, such 

 as chloride of ethyliden, only on the medulla oblongata. If tri- 

 chlorinated butylaldehyde (butylchloral) be administered to an 

 animal only an effect on the medulla oblongata is produced, in spite 

 of the triple chlorination. The reason of this is that allylchloroform 

 is formed in the organism, which, not being stable, splits up into 

 dichlorallylen, which is a bichlorinated body. 



Owing to the progress in chemistry medical science has been 

 enabled to determine the relation which certain new drugs, by 

 reason of their composition, bear to other established remedies of 

 known constitution. This has been demonstrated by Gaetano Vinci 

 in eucain, whose composition is analogous to that of cocain. Eucain 

 is a drug which is truly fitted to replace cocain on account of its 

 slighter poisonous nature, especially in the form of its lactic acid 

 salt. 



It has frequently been assumed that certain atomic groups in 

 the molecule are the bearers of a special action, and that accord- 

 ingly the bodies of a chemical series must exhibit a similar effect. 

 That is, however, by no means the case, for even formic acid and 

 acetic acid manifest markedly different biological properties. In 

 alcohols the theory is founded on the presence of a certain chemical 

 group, which is spoken of as the alcohol group. But we see this 

 group appearing threefold in glycerine, and yet no physiological 



