IMMUNIZATION WITH BACTERIOPHAGE SUSPENSIONS 535 



Rabbit No. 16; tested after two months. Lived. 



Rabbit No. 17; tested after three months. Lived. 



All the control rabbits inoculated with half the dose, that is, with 1.5 

 cc. of the Shiga culture, died in from four to seven days. 



The rabbit is, therefore, immunized against two surely fatal doses of 

 B. dysenteriae Shiga culture by the injection of a quarter of a cubic 

 centimeter of a suspension of the Shiga-bacteriophage. The antitoxic 

 immunity is estabhshed six days after the injection and persists for at 

 least three months. 



In an experiment of this kind there can be no question of the nature 

 of the process. The bacteriophage as a hving being can not be the 

 cause of the immunity. The responsible agent must be the soluble 

 principles contained in the culture medium. ^^^'^^i* 



Kabeshima^^* was the first to confirm these experiments. He in- 

 jected into the ear-vein of each of 10 rabbits, weighing about 2 kgm., 

 1 cc. of a suspension of the Shiga-bacteriophage. The suspensions 

 inoculated were of different ages, some of the rabbits receiving suspen- 

 sions which had been prepared for 3 weeks, others receiving suspensions 

 which were from 3 months to 2| years old, some of the latter being sus- 

 pensions which I had turned over to him for his experiments made in 

 my laboratory. 



Eleven days after the injections, the 10 immunized rabbits, as well as 

 10 controls, received an inoculation of 3 fatal doses of a culture of the 

 Shiga bacillus. The 10 controls died within 12 hours. All of the im- 

 munized animals resisted, and, although they became somewhat emaci- 

 ated they regained their original weight within periods of from 2 to 17 

 days. 



Kabeshima then attempted to determine at what time the immunity 

 appeared. (Naturally, in this case it is an antitoxic immunity.) Each 

 of 10 rabbits received an intravenous injection of 1 cc. of a Shiga- 

 bacteriophage suspension. They were then inoculated, one by one, 

 after variable lengths of time, with a surely fatal dose of the Shiga bacil- 



* Several immunizing experiments with the bacteriophage for B. typhosus 

 and for the paratyphoid organisms have been performed upon laboratory animals, 

 both rabbits and guinea pigs. In all cases these showed a perfect immunization; 

 — provided it is permissible to employ the word immunization when the process 

 is carried out in refractory animals. 



Not attributing any value to e.xperiments of this type I have not included them 

 in the monograph. In all cases the bacteriophage administered, either when 

 given by subcutaneous injection or by the buccal route, has been isolated a few 

 hours later from the intestinal tract. 



