530 A CONTRIBUTION TO THE STUDY OF THE PRECIPITINS, 



General Hemar-ks on the Methods employed. 



Tlie precipitin antisera were produced by the intraperitoneal 

 injection of the serum, egg-white or solution containing protein 

 into rabbits. In a few instances cats were employed. Sub- 

 cutaneous and intravenous injections were attempted, but these 

 methods of administration were not satisfactory. The rabbits 

 were well fed, and frequently gained weight during immunisa- 

 tion. The large amount of food eaten was noticed. A rabbit 

 weighing 1200 gm. would eat 400-600 gm. carrots in 24 hours. 

 The rabbits were not fed on the day of injection until after 

 the injection had been made. Daring the last three years the 

 precaution of washing and shaving the rabbits' skins has been 

 dispensed with. It was, however, of great importance that the 

 syringe, needle, and fluid to be injected should be free from 

 noxious organisms. The needle and syringe were rinsed in boil- 

 ing water immediately before each injection. This simple l)ut 

 efficient method has much diminished the time of injecting the 

 rabbits, so that twelve rabbits can be injected in a few minutes. 

 Injections were at first made every 4 or 5 days, but expei'ience 

 soon showed that an injection every second day was well 

 tolerated. In the last few immunisatjons daily injections were 

 em|)loyed. The rabbits were weighed daily, and a sudden fall of 

 weight was regarded as a sign to avoid injection for a day or 

 two. The amount injected varied with the material Ui-ed. Egg- 

 white antisera seemed more powerful when the total amount of 

 egg-white injected was large, so that lOc.c. or 20 c.c. were given 

 at each dose. With blood sera care had to be taken with the 

 initial injections, which were usually 3 c.c. to 5 c.c. If the 

 animal did not lose weight, the dose was increased to 10 cc. From 

 six to eight injections were given. As very powerful antisera 

 were obtained with five or six injections of small amounts of 

 protein, making the total amount injected as 0*2 to 0"3 gm. dried 

 protein equal to 2 to 3 c.c. blood serum, it was evident that the 

 quantity of protein injected did not necessarily determine the 

 amount of precipitin in the antiserum. 



