Intravenous Injections of Diamino-Acridine Sulphate. 139 



Method of the Tests. — The toxicity for mice was determined by injecting 

 watery solutions subcutaneously, the dose being so arranged that a 20-grm. 

 mouse received a volume of 1 c.c. ; to animals of other weights corresponding 

 volumes were given, but mice not exceeding the limits of 15-25 grm. were 

 selected for the tests. 



The bactericidal concentration was found thus : The substance to be tested, 

 in a volume usually not exceeding O'l c.c, was added to small test-tubes 

 containing 1 c.c. of the culture medium, which consisted in one series of 

 07 per cent, of peptone water, and in the other of undiluted serum, usually 

 from the ox (previously heated at 56° C. for an hour), and then 01 c.c. of a 

 1 : 20,000 dilution in saline of a peptone water culture (previously incubated for 

 24 hours at 37° C.) was added. A control was made with peptone water or serum 

 without antiseptic ; one loopful of this mixture, when stroked immediately 

 on agar, yielded about twenty colonies of Staphylococciis or B. coli. The 

 tubes were then placed at 37° C, and were examined at the end of 

 24-48 hours, in order to determine the concentration of antiseptic which 

 killed the organisms introduced ; the development of*- turbidity, of course, 

 indicated the occurrence of definite proliferation of the bacteria, but sub- 

 cultures were made also on agar and in peptone water. The results of both 

 methods of subculture corresponded in general, but it was sometimes found 

 that cultures containing antiseptic which showed no turbidity after incubation, 

 and in which, therefore, little or no multiplication of organisms had occurred, 

 still contained living bacteria. 



It is to be noted that we selected the quantity of bacteria employed for the 

 inoculation dose because, when added to the standard volume of fluid used in 

 ou.r tests (1 c.c), one loopful of the mixture yielded a convenient number of 

 colonies (about twenty) for estimating subsequent increase or decrease. But 

 the employment of 0"1 c.c. of undiluted culture, i.e. a 20,000-fold dose, 

 required for sterilisation a concentration of antiseptic only 2^-5 times 

 greater than that recorded above. 



Diamino-methyl-acridinium chloride was prepared by Benda for Ehrlich 

 and was found to possess very marked curative properties for experimental 

 trypanosome infections, hence the name " trypaflavin " was applied to it. 

 The remarkable properties of this substance and other acridiue compounds 

 as bactericidal agents, so far as we know, was not suspected. It is of 

 interest, in regard to the relationship existing between chemical constitution 

 and therapeutic action, that the trypanocidal property depends greatly on 

 the presence of the methyl-group attached to the nitrogen atom. This is 

 implied, though not expressly stated in Benda's work. 



VOL. xc. — B. 



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