176 CHEMICAL NATURE OF ANTIBIOTIC SUBSTANCES 



by different workers to different preparations even when these have 

 been obtained from the same organism. Witness, for example, the 

 designation "subtilin" that has been applied in different countries to 

 preparations obtained from different strains of members of the B. suh- 

 t'tlis group grown on media of different composition. The fact that other 

 names, like "bacitracin," "subtilysin," "endo-subtilysin," and "bacillin," 

 are given to certain preparations of B. sub tilts does not necessarily 

 indicate that the substances are different. We must await further in- 

 formation concerning the chemical and biological properties of these 

 preparations before their identity can be definitely established. The 

 name "aspergillin" has been applied to at least four preparations, in spite 

 of the fact that it was first used to designate the black pigment of A . 

 niger. 



Various names have been used to designate indefinite preparations 

 produced by unknown organisms. This is true, for example, of "my- 

 cocidin" produced by certain fungi and active against M. tuberculosis 

 (328), and of "fungin" and "my coin," terms used to designate anti- 

 biotics of fungi and actinomycetes, as well as of the term "inhibin" to 

 designate antibacterial substances present in honey. 



On the basis of their solubility, antibiotics may be divided into four 

 groups : 



Group A. Soluble in water at different reactions, and insolutle in ether. 

 These substances usually represent proteins, organic bases, or adsorp- 

 tion compounds on protein molecules. Some have been isolated in a 

 pure state. They comprise the bacterial enzymes acting upon micro- 

 bial polysaccharides, actinomycetin, microbial lysozyme, streptothri- 

 cin, streptomycin, penatin, and pyocyanin. 



Group B. Soluble in ether and in water at proper reactions. Here belong 

 many of the important antibiotic substances so far isolated and de- 

 scribed, namely, penicillin, flavicin, citrinin, clavacin, proactinomy- 

 cin, penicillic acid, and aspergillic acid. 



Group C. Insoluble in ether and in water. These include gramicidin, ty- 

 rocidine, subtilin, and simplexin. 



Group D. Soluble in ether and insoluble in water. These include fumi- 

 gacin, fumigatin, gliotoxin, actinomycin, pyocyanase, and others. 



Some of the antibiotic substances have been crystallized, and infor- 



