IMMUNIZATION WITH BACTERIOPHAGE SUSPENSIONS 529 



sidered as a living being. Aside from the dissolved bacterial sub- 

 stance do the other substances present in the culture play any part in 

 the production of immunity? In the present state of these investiga- 

 tions it is impossible to affirm or deny this. 



We have tested the action of temperature on the immunizing ele- 

 ment contained in the bacteriophage suspension. To this end, we 

 have repeated the experiment of the bacteriophage treated with gly- 

 cerine, with the difference that the suspension was previously subjected 

 to a temperature of 56°C. maintained for a half hour. Two steers 

 have each received a dose of this preparation heated and glycerinized, 

 corresponding to 0.25 cc. of the original suspension. After forty-five 

 days they were tested, the one with five, the other with fifty, fatal 

 doses of barbone culture. The first resisted, the second died. The 

 immunizing principle contained in the bacteriophage suspension is not 

 destroyed but is sensibly weakened by heating for a half hour at 56°C. 



Although it is not yet possible to know with certainty the nature of 

 the process which controls the development of organic immunity, 

 we are at least able to recognize the result and to note the property 

 which distinguishes the animal immunized by an injection of the 

 bacteriophage from a normal animal. 



In the case of the immunity acquired as a result of an attack of a 

 contagious disease the blood possesses preventive properties. The 

 blood of immunized animals enjoys the same property, as the following 

 experiments show. 



I. Steer No. 54 received on November 5, 0.25 cc. of a Barbone- 

 bacteriophage. Fourteen days later 500 cc. of blood was taken into 

 a flask containing 25 cc. of a 10 per cent solution of sodium citrate. 

 The blood was immediately injected into the jugular vein of steer No. 

 43. This last animal was tested twenty-three hours later by the in- 

 jection of 1000 fatal doses of the bacterium of barbone culture. It 

 failed to show the least evidence of infection. A control died in twenty- 

 three hours. Steer No. 54 likewise resisted the inoculation of 1000 

 fatal doses, given on December 1st. 



II. The experiment given above was repeated. Steer No. 112 re- 

 ceived into the jugular vein 500 cc. of blood from steer No. 95. Both 

 of them resisted the test injections. 



III. Steer No. 104 received on December 29 a subcutaneous injec- 

 tion of 0.04 cc. of a suspension of the bacteriophage. Four days later 

 500 cc. of blood were taken as before and this was transfused into 

 steer No. 108. The next day the two steers resisted the inoculation of 

 five fatal doses, which killed the control animal in thirty-two hours. 



