sraixd one hour at room temperature before being injected into the 
guinea pig.® Not one of the 50 guinea pigs receiving this mixture 
died acutely of toxin poisoning. 
Ail the guinea pigs receiving an injection of 250 units of the diph- 
theria antitoxin at intervals of 4, 8, 12, 16, and 20 hours after infec- 
tion were protected against paralysis. The two guinea pigs (Nos. 
8124 and 8125) receiving 250 units of antitoxin twenty-four hours 
after infection developed slight paralysis on the twenty-fifth day; 
later dian the controls. They made a complete recovery. 
The guinea pigs (Nos. 8138, 8139, and 8140) which received 2,000 
units of antitoxin twenty-fqur hours after infection developed very 
slight paralysis, from which they recovered. It was noticeable that 
the guinea pigs which received 2,000 units twenty-four hours after 
infection developed a somewhat milder type of paralysis than those 
which received 250 units. 
Further, the guinea pigs (Nos. 8130 and 8131) receiving repeated 
injections of 250 units beginning 24 hours after infection developed 
but slight paralysis. 
From the first series we also learn that 1 unit of antitoxin given 
before or at the time of infection is sufficient to prevent the develop- 
ment of paralysis. On the other hand, as much as 2,000 units, given 
24 hours after infection, did not prevent the development of this 
sequel, although it modified the severity of the palsy and saved life. 
c^For details of the technic, see Hygienic Laboratory Bulletin No. 21, “The im- 
inimiiy unit for standardizing diphtheria antitoxin (based on Ehrlich’s normal serum); 
official standard prepared under the act approved July 1, 1902.” M. J. Rosenau. 
