■92 THE VENOM OF HELODERMA. 



PRECIPITINS IN THE SERUM OF RABBITS IMMUNIZED AGAINST 

 HELODERMA VENOM. 



We mixed the blood of the rabbits which had been immunized against 

 venom with various quantities of fresh venom, dried venom, or dried heloderma 

 blood, and noted the appearance of precipitates in these mixtures. We used 

 in these experiments the serum of two of the immune rabbits, X 1 and Z 4, at a 

 time when they were able to resist an injection of 100 mg. and 95 mg. of venom, 

 respectively. In the following table the results of these experiments are given : 

 Precipitins in serum of rabbits immunized against heloderma venom. 



•Serum of rabbit X 1. tSerum of rabbit Z 4. 



The serum of the immunized rabbits contains venom precipitins. How- 

 ever, the serum of normal rabbits may also contain precipitins for the venom, 

 but not in such large quantities as the immune serum. The serum of rabbit 

 XI contained more precipitin than the serum of rabbit Z4. 



In view of the fact that the smaller quantities of serum reacted more 

 rapidly with the venom than the larger quantities of .serum (experiments with 

 serum of rabbit XI), we may conclude that there is an optimum proportion 

 for mixtures of the venom and immune serum. However, the degree of pre- 



