370 BACTERIOLOGY. 



duction the neutralizing value of the fatal dose increases 

 steadily until it becomes five to ten times its original 

 amount. 



In our experiments the greatest value for L+ was 

 126, the least 27. As at six hours L+ was only 72 

 and at twenty-eight hours only 91, we doubt whether 

 L^ ever reaches above 150. 1 When we seek to analyze 

 the above-described process we find certain facts which 

 seem partly to explain it. Experiments have shown 

 that filtered toxin, preserved for any length of time in 

 conditions under which access of air occurs, gradually 

 loses in both its toxicity and neutralizing power, and 

 that it loses more rapidly in the former property than 

 in the latter. Thus, while the fatal dose of a toxin pre- 

 served for one year rose from 0.01 c.c, to 0.55 c.c., it 

 lost only half as much in neutralizing value, 1 unit 

 neutralizing at first 1 c.c., at the end of the year 0.25 

 c.c. These processes take place more rapidly at room- 

 temperature than in the ice-chest, and in the incubator 

 than in the room. 



In the fluid holding the living bacilli we have, there- 

 fore, after the first few hours of toxin formation, a 

 double process going on one of deterioration in the 

 toxin already accumulated, which tends to increase the 

 neutralizing value of the fatal dose; the other of new 

 toxin formation, which probably tends to diminish the 

 neutralizing value. The chemical changes produced 

 by the growth of the bacilli in the bouillon tend to aid 

 one or the other of these processes, and so to make, from 

 hour to hour, slight changes in the value of the fatal 



1 Li = fatal doses of toxin required to kill a guinea-pig in four days after 

 having been mixed with one unit of antitoxin. 

 L = fatal doses of toxin required to fully neutralize one unit of antitoxin- 



