THE BIOLOGICAL ACTIVITIES OF BACTERIA 73 



tion of a variation in the cultures of Colon bacilli in which a variant 

 producing an autolytic enzyme is developed, and this property of 

 autolysin production is then inherited from culture to culture. Con- 

 ceived in this way, the lytic principle would be regarded as the 

 inheritance of an acquired characteristic. 



In our own laboratory we have isolated a lytic principle by the 

 D'Herelle technique described above, from the stool of a typhoid 

 convalescent. It corresponds in most details to the lytic principles 

 described by D'Herelle. It is filtrable, thermostable, and transmit- 

 tible in series. It is both inhibitory and lytic, that is, a small amount 

 of the original stool filtrate or any one of the subsequent generations 

 will prevent growth of a heavily inoculated tube, or dissolve a young 

 turbid broth culture. This lytic principle is only active against 

 closely allied species of bacteria of the typhoid-paratyphoid and 

 dysentery groups. In the earlier experiments this lytic principle 

 did not appear active against paratyphoid "A" or "B," but when 

 retested recently, it was also active against these organisms. It has 

 no action against cholera, B. pyocyaneous or B. coli, or against 

 staphylococcus or pneumococcus. 



Unlike the lytic principles described by D'Herelle, the one 

 isolated by us has not increased in potency in the course of the 

 generations through which it has been passed. It differs also from 

 those described by D'Herelle in that it usually does not sterilize 

 the dissolved culture completely. On sub-culturing a small number 

 of colonies develop which are of two types: one a round typical 

 typhoid colony, the other irregular in outline. The latter type was 

 first described by Bordet in connection with the lytic principle that 

 he was able to produce against B. coli by intraperitoneal injections 

 of guinea pigs, and the bacilli composing these irregular colonies 

 were shown by him to be the bearer of the lytic principle. 



The typical colonies which develop from plating a dissolved cul- 

 ture, on restreaking, give only regular colonies. If, however, one 

 of the irregular colonies are restreaked both regular and irregular 

 colonies will develop. Daily restreaking of irregular colonies have 

 failed to eliminate the typical normal colony in a series of 15 

 generations and the irregular colonies continued to carry the lytic 

 principle. If one of these typical typhoid colonies is fished with 

 broth, the broth will become cloudy after incubation. Broth fishings 

 of the irregular colonies will, however, often remain clear after 

 12 to 18 hours incubation and the lytic principle is then present in 



