138 Messrs. Browning and Gulbransen. Effect on Blood of 



similar in its action. The relative lack of toxic effect on leucocytes is shown 

 by the fact that when a volume of human " leucocyte cream " along with a 

 volume of human serum, the mixture containing 1 : 10,000 of the acridine 

 derivatives, is incubated for two hours at 37° C, and staphylococci afe subse- 

 quently added — time then being allowed for phagocytosis to occur — an 

 estimation of the phagocytic count yields over 50 per cent, of the number 

 of cocci ingested hj leucocytes subjected to similar conditions except that 

 the dye was omitted from the mixture ; on the other hand, 1 : 10,000 of 

 mercuric chloride reduces the phagocytic power to a much greater extent. 

 Now in the case of the mercury salt in serum, this concentration represents 

 practically the limit beyond which effective antiseptic action does not take 

 place ; on the other hand, the acridine compounds in 1 : 10,000 dilution in 

 serum are powerfully antiseptic and ultimately prove lethal to the organisms. 



Experiments have shown that of the two substances diamino-acridine 

 sulphate* is the more suited for direct injection into the blood stream, as it 

 is less toxic and has less agglutinating action on the red blood corpuscles 

 than diamino-methyl-acridinium chloride. Accordingly, the present investi- 

 gation was undertaken with a view to ascertaining whether it was possible 

 to render the blood serum antiseptic without at the same time damaging the 

 health of an animal treated in this fashion ; the results have shown that 

 this aim could be realised. 



The following preliminary observations, the results of which are shown in 

 the Table, served to determine the relative toxicity of diamino-acridine 

 sulphate and diainiuo-methyl-acridiniimi chloride, and also their bactericidal 

 power for Staphylococcus aureus and B. coli. 



Substance. 



Maximum 

 non-lethal 

 dose for a 

 normal 

 20-grm. 

 mouse. 



Bactericidal concentration for 



Staph, aureus in 



B. coli (Escherich) in 



'V-per-cent. 



peptone 

 water. 



Serum. 



"V-per-cent. 



peptone 

 water. 



Serum. 



Diamino-acridine sulphate... 



Diamino-methyl-acridinium 

 chloride 



grm. 

 -003 



-0006 



1 : 20,000 

 1 : 20,000 



1 : 200,000 

 1 : 200,000 



1 : 4000 

 1 : 1300 



1 : 100,000 

 1 : 100,000 



* We have pleasure in expressing our indebtedness to Drs. Barger and Ewins, of the 

 Department of Biochemistry and Pharmacology of the Medical Research Committee, 

 for their kindness in preparing for us the supply of this substance which we required. 



