CHEMOTHERAPY 



139 



results in bacteriostasis is known as the antibacterial 

 index, or bacteriostatic, constant. It varies, with any 

 particular drug, from organism to organism, and with a 

 particular organism from dnig to drug. These variations 

 in value are proportional to the potency of a drug against 

 the organism, as measured by the minimum bacterio- 

 static concentration in vitro. These findings are illustrated 

 in the following tables, from the work of Wyss, Grubaugh 

 and Schmelkes (Proc. Soc. Exp. Biol Med. 49 (1942) 618). 



Table 9 



Concentration of sulphonamides permitting 50 per cent, of the maximum 

 growth in 16 hours. 



Table 10 



Effectiveness of drugs in overcoming ^-aminobenzoic acid. 



