408 COLLECTED STUDIES IN IMMUNITY. 



and that it increases with the number of these groups: thus sulfonal, 

 (CH 3 ) 2 .C-(S0 2 C 2 H 5 ) 2 , and trional, CH 3 C 2 H 5 -C- (S0 2 C 2 H 5 ) 2 . Of 

 the other hypnotics which owe their action in part to the ethyl group 

 I may mention amylenhydrate, C(CH 3 ) 2 (C 2 H 5 ) -OH, and ethyl ur- 

 ethan, NH 2 CO OC 2 H 5 . The influence of the ethyl radical is further- 

 more clearly shown in another series of combinations. In an artificial 

 sweetening substance, dulcin, which is about two hundred times sweeter 

 than sugar, this influence is very evident. This substance is phenyl 

 urea ethoxylated in the para position, C 2 H 5 0-C6H4-NH CO-NH 2 . 

 Since neither simple phenyl urea nor the methoxy combination, 

 CH 3 -0-C6H 4 -NH-CO-NH 2 , analogous to dulcin, possesses any sweet 

 taste whatsoever, we are forced to conclude that this is due to a function 

 of the ethyl radical. Of the "remedies containing the ethyl radical 

 there may still be mentioned phenacetin, C 2 H 5 O CoH 4 NH CO CH 3 , 

 and two anaesthetics, holocain, C 2 H 5 -O-C6H 4 -NH-C(CH 3 ): 

 N CeH4 OC 2 H 5 , and acoin, all three of which are derived from 

 phenetidin. It is significant that of the entire series of alcohols 

 only ethyl alcohol has become established as a beverage, and that 

 since the earliest time attention was directed to producing it as pure 

 as possible, i.e., to free it from higher and lower relatives. In all 

 of these examples we are dealing with an influence on the nervous 

 system, the central system (sulfonal ethylurethan, amylen hydrate, 

 alcohol), as well as the peripheral endings (dulcin, anaesthetics). 

 Hence we shall probably not err if we assume that the ethyl group 

 possesses a certain relation to the nervous system. In this con- 

 nection an observation which I made in conjunction with Dr. Michaelis 

 may perhaps be of some significance. We were studying a blue-green 

 azo dye which is formed by the combination of diazotated diethyl- 

 saffranin and dimethylanilin, and which therefore is expresed by 

 the formula 



N = N 



\ 



N(CH 3 ) 2 



It was found that this substance has the power, somewhat like 

 methylene blue, to stain the nerve endings of living (?) tissue organs, 



