90 THE VENOM OF HELODERMA. 



anaphylaxis were present. Other investigators have made similar observa- 

 tions in the immunization against snake venoms.* 



Blood taken from two of the rabbits (X 1 and Z 4) was tested for the pres- 

 ence of precipitins. Furthermore, the protective action of the serum obtained 

 from these animals was tested against venom and mixtures of venom and of 

 serum obtained from the immunized rabbits were injected into mice. 



PROTECTIVE POWER OF THE SERUM OF IMMUNIZED RABBITS. 



Mice were used in testing the protective power of the serum of immunized 

 rabbits. 



Some blood was drawn from rabbit Z 4 after it had withstood the injection 

 of 95 mg. of venom in one dose and after it had been under treatment for four 

 and a half months. This blood was allowed to clot and the serum was drawn 

 off after the blood had stood in the ice-box over night. 



Mice were injected with venom, venom and immune serum, and venom 

 and normal-rabbit serum. Injection of 0.02 c.c. of fresh venom killed a mouse 

 in 35 minutes, 1 c.c. of normal-rabbit serum added to the venom killed a second 

 mouse in 20 minutes, while a mouse injected with a similar quantity of venom 

 which had stood for an hour mixed with 1 c.c. of immune-rabbit serum died 

 after 3 hours. 



The results were practically the same when we first injected the serum and 

 then the venom as when they were injected together. Thus control mice in- 

 jected with either 0.015 or 0.01 c.c. of fresh venom died somewhat sooner than 

 mice which received similar quantities of venom but which had, in addition, 

 received 1 c.c. of either normal or immune-rabbit serum; the animals which 

 received the immune serum lived a little longer than those which received the 

 normal-rabbit serum in addition to the venom. When we injected 2 c.c. of 

 serum, followed, in 40 minutes, by the injection of 0.01 c.c. of fresh venom, we 

 found that the animal which received immune-rabbit serum and venom lived 

 longer than a mouse which received venom alone, or a mouse which received 

 2 c.c. of normal-rabbit serum followed by 0.01 c.c. of fresh venom solution. 

 This mouse died as soon as the control animal. 



The same rabbit whose serum was tested in the above experiments (Z4) 

 was bled again a few days later before any further injections of venom had been 

 made. At this time only a very small quantity of blood was drawn. In all 

 the experiments with this serum the mice received 0.01 c.c. of fresh venom. 

 Two quantities of serum were used, namely, 1 c.c. and 1.5 c.c. of either the 

 immune-rabbit serum or the normal-rabbit serum. All the six mice used in 

 these experiments, those injected with venom alone as well as those injected 

 with venom plus serum, died in approximately the same length of time. 



The other rabbit (XI) was bled 4 months after the injections were begun, 

 when it had developed sufficient resistance to withstand the injection of a dose 

 of 100 mg. of venom. In these experiments mice were injected M'ith venom 

 alone, with venom and normal-rabbit serum, and with venom and immune- 



•Immunization with heloderma venom might perhaps be more easily accomplished if it were possible to sepa- 

 rate venom and proteid material through heating, as can be done in thecaaeof cobra venom. This would obviate the 

 necessity of injecting accessory proteids that may add to the local anaphylactic condition. 



