40 ACTIVE IMMUNIZATION. 



b. Rapid Immunization. 



Rabbit II. 



8./IV. 1905 Injection of 4 c.c. of natural swine pest aggressin subcutaneously. 

 lo./IV. Animal somewhat depressed. 



I3./IV. Perfectly active. 



26. /IV. ist infection: i/io loopful of swine pest culture subcutaneously. 



i6./VI. 2d infection: i loopful of swine pest culture subcutaneously. 



Animal remained active. 



Controls. 



Rabbit III. 



26. /TV. 1905 1/10,000 loopful of swine pest culture subcutaneously. 

 2 7 ./IV. t- 



These experiments prove conclusively that by the method described above, 

 it is possible to attain a high grade of immunity. In this connection, how- 

 ever, it is very important to adhere to what Bail pointed out, namely, that 

 a long period should elapse between the last inoculation with the aggressin and 

 the first infection; the reason for that being, that during the period of immuniza- 

 tion, and following it for a longer duration of time, there is a condition of 

 hyper susceptibility to infection. 



Example of Active Immunization with Artificial Aggressins. 



Rabbit i. 



3./VI. 1905 ist injection: 4 c.cm. of watery extract of swine pest bacilli subcutaneously. 

 I4./VL 2d injection: 2 c.cm. of watery extract of swine pest bacilli subcutaneously. 



25. /VI. Removal of some blood. 



4./VII. 3d injection; 3 c.cm. of watery extract of swine pest bacilli subcutaneously. 



21 /VII. Infection: i/io loopful of swine pest culture subcutaneously. 



3-/X. Animal alive and healthy. 



Rabbit 2. 



19. /VI. 1905 ist injection: 2 . 5 c.c. of serous extract of swine pest bacilli subcutaneously. 

 9. /VII. 2d injection: 2 . o c.c. of serous extract of swine pest bacilli subcutaneously. 



12. /VII. 3d injection: 4. o c.c. of serous extract of swine pest bacilli subcutaneously. 



24. /VII. ist infection: i/io loopful of swine pest culture subcutaneously. 



22./IX. 2d infection: i loopful of swine pest culture intravenously. 



Animal remains perfectly well. 

 Rabbit 3. 



i6./VI. 1905 Injection: 2.5 c.c. of watery extract of swine pest bacilli subcutaneously. 

 4./VII. Infection: i/ioo loopful of swine pest culture subcutaneously. 



15. /VII. Small local infiltrate. Very active. 



3-/X. Animal alive and perfectly well. 



Control animals inoculated on the days of infection died within twenty-four hours 

 after inoculations of 1/100,000 loopful of culture intravenously, 1/10,000 loopful 

 subcutaneously. 



It is evident from the above, that an immunity against pure parasites can 

 be obtained just as well by one or several injections of extracts of living bac- 



