ANTISEPTICS 



165 



and tyrocidin, two different substances produced by the 

 same Bacillus hrevis, have been obtained in crystalline 

 form by Dubos (1939-40) and have molecular weights 

 of about 900 to 1400 but their structure has not yet been 

 determined. The penicillin of Penicillhim notatum is so 

 unstable that its structure is also unknown. This sub- 

 stance retains its activity only at low temperatures ; how- 

 ever, stable and fairly efficient esters have been obtained 

 (Meyer et al., 1943)/ 



It is not probable that substances so different in na- 

 ture will act upon bacteria in the same manner. How- 

 ever, little can be said about their mode of action. They 

 cannot be included in any of the groups of antiseptics 

 already discussed because their chemical nature is too 

 uncertain. Most of them are highly selective, as has been 

 stated above for gramicidin and penicillin (they are 

 good antiseptics, but not strong disinfectants). Penicil- 

 lin will inhibit a few species at a concentration of 1 ppm., 

 but others not even at 1000 ppm. (Abraham et al., 1941 )^ 

 Table 84 gives some of the data by Waksman and Wood- 



TABLE 34 



Growth-inhibiting concenti-ations (in parts per million) of various 

 anti-biotic substances. (From Waksman and Woodruff, 1942.) 



*Total active material from Bacillus hrevis, containing gramicidin 

 and tyrocidin. ,..-— 



1. See also p. 124. 



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