230 DISEASE CONTROL 



tions of 0.25 and o.i per cent j the application was continued for 2 to 4 

 days (780). 



Since penicillin readily loses its activity in an acid solution, it is used 

 in the form of the sodium salt. Rabbits excreted in the urine as much as 

 50 per cent of the penicillin after intravenous injection, but less than 

 20 per cent after administration into the intestine j some excretion took 

 place in the bile. The penicillin could not be detected in the blood 

 within one-half hour after administration. Cats differed in this respect 

 from rabbits, since they maintained an antibacterial concentration of 

 penicillin in the blood for at least 1.5 hours after subcutaneous or intra- 

 venous injection, and for at least 3 hours after intestinal administration. 

 They differed also in excreting about 50 per cent of the penicillin in the 

 urine, even when the substance was injected into the intestine. In this 

 respect man appeared to resemble cats more closely than rabbits. The 

 excretion of penicillin could be blocked by simultaneous administration 

 of diodrast (723-725). 



A comparison of antibiotic agents against the anaerobes causing gas 

 gangrene placed tyrothricin in first place, followed successively by peni- 

 cillin, the sulfa drugs, and other antibiotic agents j however, in vivo 

 treatment of mice infected intramuscularly with CI. ferfringens placed 

 penicillin first, with tyrothricin and aspergillic acid at the bottom of the 

 list (562)- Penicillin also proved superior to sulfonamides and amino 

 acridines in experimental infection with CI. welchii and CI. aedematiens 



The in vivo activity of penicillin against CI. se-pticum and other 

 anaerobes, as well as many other bacterial pathogens ( 1 1 3 ) , is brought 

 out in Table 41. A single subcutaneous treatment of mice with 50 

 Florey units of penicillin at the time of intramuscular inoculation with 

 CI. welchii protected 98 per cent of the infected animals, and repeated 

 small doses gave as good protection as a single large dose. Delay in the 

 institution of therapy lowered the survival rate, but not appreciably un- 

 less the delay was over 3 hours. Local lesions were completely healed 

 within 3 weeks if penicillin was injected repeatedly into the site of in- 

 fection (371). 



An intravenous injection of 20 mg. of the sodium salt of penicillin 

 was without apparent effect on a mouse, and human leukocytes survived 



