BACTERIOPHAGOUS ANTISERUM 133 



Experiment XLIII. Four mice receive subcutaneously a dose of toxin 

 equal to one-tenth of the lethal dose. The first is held as a control. Two 

 others receive 0.2 cc. of the bacteriophage-Shiga antiserum, the last 0.1 

 cc. of this serum. The first remains perfectly well indefinitely. The two 

 which received the 0. 2 cc. dose of serum die after 40 hours, and the last one 

 after fifty-four hours. 



This experiment proves that the bacteriophage-Shiga anti- 

 serum sensitizes the animal to the action of the toxin. It should 

 be stated here that whatever the number of lethal doses of the 

 toxin of Nicolle injected into a mouse, death never occurs before 

 the fourth day. Here, when the antibacteriophage serum is 

 added to the toxin, even to a dose below the minimal lethal dose, 

 death takes place within forty-eight hours. 



Instead of toxin, let us take living dysentery bacilli and see the 

 effect of the antiserum on injections of this nature. 



Experiment XLIV . Four mice receive subcutaneously a dose of dysen- 

 tery bacilli equal to one-fifth the lethal dose. The first mouse is held as a 

 control. The second receives, subcutaneously, 0. 2 cc. of the antibacterio- 

 phage-Shiga serum, the last two 0. 1 cc. of this serum. The control animal 

 lives, showing nothing abnormal. Those which at the same time received 

 the serum die in seven to nine days after the injection, after showing during 

 the last twenty-four hours a paralysis of the posterior extremities. In 

 general, mice do not show this symptom after the injection of B. dysen- 

 teriae; only the rabbit shows this particular symptom. 



The result is clear-cut; in all cases the antibacteriophage-Shiga 

 serum is sensitizing. This is, incidentally, the first example of 

 an anti-immunizing serum. 



It is possible that the antibacteriophage-Shiga serum actually 

 contains an antitoxin but that this is masked by the presence of 

 a powerful "sensibilisine." This is the more plausible, for we 

 shall see in the chapter dealing with immunization, that rabbits 

 which have received but a single minute injection of a culture of 

 the antidysentery bacteriophage are effectively vaccinated against 

 the effects of the toxin. The sensibilisine develops in the animal 

 only after the second injection. This condition is not peculiar 

 to the case of dysentery ; we find it again when we consider immuni- 

 zation against barbone. 



This phenomenon of sensitization invites much further investi- 

 gation, which will permit, without doubt, an extension of our 



