70 METHODS FOR EFFECTING ACTIVE IMMUNIZATION OF ANIMALS 



PRODUCTION OF PREdPITINS 



Precipitin immune serums are frequently of value in making a differ- 

 entiation of the proteids, as in the examination of blood-stains, meat, 

 milk, cheese, etc. They are usually prepared by immunizing large 

 rabbits with injections of the sterile antigen. Injections may be given 

 intravenously or intraperitoneally, the former usually yielding the more 

 potent serums. 



Any foreign serum may be used in the preparation of precipitins, 

 such as that of the human, horse, ox, dog, cat, guinea-pig, etc. To pro- 

 duce an antirabbit precipitin a guinea-pig is immunized by intraperi- 

 toneal injections of rabbit serum. An antihuman precipitin serum of 

 high titer is usually obtained with difficulty. It is good practice to 

 immunize a number of rabbits with each antigen, as some animals will 

 produce no precipitin whatever the method used. 



In preparing precipitins for the purpose of identifying blood-stains 

 whole blood may be injected. It is better, however, to use serum only, 

 as the immune serum may be used in diagnosis, according to the method 

 of complement fixation, when the presence of hemolysin is not advisable. 



Serum Precipitins (Intravenous Method). First Method. Three 

 injections are given of 5, 10, and 15 c.c. on each of three successive 

 days, and the animals are bled twelve days after the last injection has 

 been made. 



Second Method. One injection of 30 c.c. of serum may be given, and 

 followed twelve days later by bleeding. 



Third Method. A slower method consists in giving the injections at 

 intervals of a week. After the third dose a few cubic centimeters of blood 

 are withdrawn from the ear, and the serum titrated, as rabbits are most 

 prone to succumb after the third dose, and in many instances the serum 

 is of such strength as to require no further immunization. The ani- 

 mals are bled one week after the last injection has been given. 



Doses may be given as follows : 



First dose: 10 c.c. serum intravenously. 

 Second dose: 8 c.c. serum intravenously. 

 Third dose: 5 c.c. serum intravenously. 

 Fourth dose: 5 c.c. serum intravenously. 

 Fifth dose: 3 c.c. serum intravenously. 



Fourth Method. Rabbits may be immunized by making intra- 

 peritoneal injections after any of the foregoing methods, and with the 

 same or slightly larger doses. 



