284 DISEASE CONTROL 



about some protection of the cells from the effects of these substances 



(144). 



When given intravenously in a 9.5 per cent alcoholic solution, tyro- 

 thricin was found (896) to be effective in the treatment of chickens in- 

 fected with Plasmodium gallinaceum'. It has a marked parasiticidal 

 effect, especially on the extracellular merozoites produced at segmenta- 

 tion. Prolonged daily treatment of 100 gm. chickens with 0.2 mg. of 

 material from the beginning of infection lengthens the incubation 

 period of blood-induced infections, lowers the peak of acute infection, 

 and prevents fatal relapses. When given in 12 daily doses, it has a 

 quinine equivalent of about 4, the effective dose being, however, near 

 the toxic level. Whereas tyrothricin is parasiticidal, quinine is parasiti- 

 static, the first being also more effective in inhibiting oxygen consump- 

 tion of the parasites. 



Tyrothricin is limited, because of its toxicity, to topical applications j 

 for that purpose, it has advantages over certain other antibacterial 

 agents, such as the sulfonamides and penicillin, because of its stability, 

 its wider range of antibacterial action, its activity in presence of blood 

 and serum, its low tissue toxicity, and its lack of sensitizing properties 

 (403a). It is ineffective when incorporated into common ointment 

 bases (19). 



Particularly favorable results were obtained from the use of grami- 

 cidin in the treatment of chronic mastitis (576). Several cows received 

 treatment with increasing amounts of gramicidin diluted with distilled 

 water. Following the morning milking, the residual milk in the cistern 

 and in the teat was flushed out with 100 to 200 ml. of the gramicidin so- 

 lution, containing 60 to 240 mg. in 1,000 ml. water j 800 to 900 ml. were 

 then injected under pressure into the quarter and allowed to remain 

 until the next milking. Within one hour after the injection, the treated 

 quarter became distended and rectal temperature began to increase, 

 reaching 41° C. at the fifth or sixth hour. The temperature returned 

 to nearly normal in about 3 hours thereafter, the acute swelling having 

 subsided at the next milking. The streptococci disappeared from most 

 of the quarters treated, without an appreciable decrease in milk pro- 

 duction. The fact that streptococci had been eliminated was established 



