Production of Antisera 57 



after the last injection. Continental workers have used quantities 

 ranging to hundreds of c.cs., and have frequently found that their 

 animals stood the operation badly, whereas the above animal, and most 

 of the others we have treated, continued to gain weight, and appeared 

 to be healthy. Some of our control antisera was prepared by the intra- 

 peritoneal method and quantities ranging from 30 to 60 c.c. were used. 

 The animals stood the treatment very well." 



The fact that long-continued treatment of rabbits leads to the dis- 

 appearance of precipitins from the blood has been already noted by 

 Tchistovitch (1899) in rabbits rendered immune to eel serum. I was 

 able to confirm this (16, xii. 1901) in rabbits treated with ox and sheep 

 serum, the treatment having been too prolonged. As I stated in my 

 paper, just cited, "There is therefore a point in the treatment of 

 animals, when, for purposes of obtaining an antiserum, a maximum 

 of reaction is reached and the animal should be bled ; this can be 

 determined by periodic bleedings from the ear-vein." 



Mode of Injection. 



If the serum to be injected has been preserved by means of 

 chloroform, as is frequently the case, it is desirable to remove as much 

 of this as possible, as the injection may prove fatal from the chloroform 

 contained in the serum. This is best accomplished by pouring the 

 serum into Petri dishes, these being exposed, half covered with their 

 lids, in the thermostat at 37 C. for about half-an-hour, or until no 

 perceptible odour of chloroform emanates from the serum. For intra- 

 peritoneal injections I have used an all-metal 10 c.c. syringe, one of 

 smaller capacity (5 c.c.) being used for intravenous injections. 



Intraperitoneal Injections. 



The rabbit being held by an assistant, belly up, is lathered over the 

 seat of operation by means of liquid soap containing lysol. A small 

 area about 5 cm. across is then shaved in the lower abdominal region on 

 the left side. After disinfecting the skin with lysol solution, applied 

 with cotton pledgets, a small puncture is made through the skin with 

 a fine scalpel, this facilitating the penetration of the needle of the 

 syringe, the point of which it is better to render somewhat blunt, for 

 the reason that this lessens the chance of penetrating the intestine. 

 Penetrate the abdominal wall, holding the needle at right angles to its 

 surface. Having gently bored the needle through the abdominal wall, 

 through which it passes not infrequently with a slight jerk, immediately 



