IN VIVO ACTIVITY 129 



alone, however, since a certain bacterium was isolated from the soil 

 which definitely inhibited the growth of this plant pathogen. 



Goss (347) observed that the severity of scab is dependent on the 

 amount of S. scabies present in the soil, which was believed to be con- 

 trolled by the soil microflora. No evidence was obtained as to whether 

 the effect of the soil flora on S. scabies was due to specific organisms. 

 Kieszling (502) isolated two cultures of bacteria which were antagonis- 

 tic to S. scabies; when added to the soil, these bacteria prevented the 

 development of scab on potatoes. 



IN VIVO ACTIVITY OF SUBSTANCES PRODUCED 

 BY ACTINOMYCETES 



Just as the chemical nature of the antibiotic agents produced by ac- 

 tinomycetes varies, so does the action of these agents in the animal body. 

 Some, like actinomycin, are very toxic, whereas others, like streptothri- 

 cin and streptomycin, have low toxicity and give great promise of prac- 

 tical application. Because of the activity of streptothricin and strepto- 

 mycin against gram-negative bacteria and because of the lack of reliable 

 chemotherapeutic agents active against these bacteria, the utilization of 

 these substances in the treatment of certain diseases caused by such bac- 

 teria has become very significant. Some preparations, like actinomyce- 

 tin, have been utilized in the preparation of a bacterial hydrolysate 

 (mycolysate) for vaccination purposes. Streptomycin has come to be 

 recognized as an important chemotherapeutic agent in the treatment of 

 a number of infectious diseases. 



