ANTIBIOTICS AS CHEMOTFIERAPEUTIC AGENTS 285 



by daily bacteriological examination of the milk over periods ranging 

 from 1 5 to 8 1 days. 



Sterile mineral oil was later found (577) to be a suitable, nonir- 

 ritating medium for the administration of the gramicidin, though 

 some of the cows thus treated gave severe reactions. An alcoholic solu- 

 tion (2 to 3 ml.) of 80 to 120 mg. gramicidin was emulsified in 15 ml. 

 sterile distilled water, and the emulsion mixed with 25 ml. of heavy 

 mineral oil. The mixture was injected into the cistern shortly after the 

 morning milking and allowed to remain until the evening milking. The 

 treatment was repeated for several days in succession. Of 31 quarters 

 naturally infected with Streptococcus agalactiae and treated by the 

 gramicidin-oil mixture, 16 seemed to have responded by a complete dis- 

 appearance of the streptococci. The infection in some of the cases was of 

 severe chronic nature. 



Less satisfactory results were obtained in the treatment of bovine 

 mastitis caused by Streftococcus uher'is; of 4 cases treated, only one re- 

 sponded satisfactorily. The final recommendation was the daily use for 

 four consecutive days of 20 to 40 mg. gramicidin in oil. These results 

 were confirmed by various investigators, who reported 60 to 90 per 

 cent cure after two or three treatments (622). 



A comparison of tyrothricin, trypaflavin, and novoxil for eradicating 

 5. agalactiae from infected udders showed best results for the first. In- 

 fections with S. uberis and Streftococcus dysgalactiae also responded 

 well, but not staphylococcic infections (829). The efficacy of the treat- 

 ment is influenced by several factors, namely, (a) site of chronic infec- 

 tion, (b) selection of suitable cases, and (c) stage of lactation. In some 

 experiments, as many as 90 per cent of the cases were cleared up with 

 tyrothricin (96). 



Gramicidin-like preparations were also used successfully in the treat- 

 ment of local infections in man. The active material must be used lo- 

 cally on infected cavities which do not communicate with the blood 

 stream (412), Tyrothricin has also been used (160) successfully in the 

 treatment of acute otitis media, acute and chronic mastoiditis, and acute 

 and chronic sinusitis. The substance does not damage the tissue or in- 

 terfere with wound healing. The growth of most staphylococci, strepto- 



