UTILIZATION OF ANTIBIOTIC SUBSTANCES 79 



duced by them, and the utilization of such substances for chemothcra- 

 peutic purposes involve ten distinct steps which may be briefly sum- 

 marized as follows: 



1. Enrichment of soil or water with specific organisms against which an- 



tagonists are to be obtained. 



2. Plating of the enriched or unenriched soil or water upon special bac- 



terial agar. 



3. Isolation of the antagonistic organisms from the plates or other culture 



media. 



4. Testing of the isolated culture for bacteriostatic and fungistatic proper- 



ties against a variety of bacteria or fungi. 



5. Growing the antagonist in suitable media and testing the filtrate or 



extract of the culture for the presence of the antibiotic substance. 



6. Separation and concentration of the antibiotic substance from the cul- 



ture medium, and determinations of its bacteriostatic spectrum. 



7. Chemical isolation of the antibiotic substance. 



8. Determination of the chemical nature of the active substance. 



9. Testing of the bacteriostatic and bactericidal properties of the sub- 



stance in intra. 

 10. Animal experimentation and practical application; study of toxicity, in 

 vivo activity, and therapeutic action. 



