170 THE VENOM OF HELODERMA. 



VIII. Heated horse or turtle serum, both of which activate venom, do not 

 inhibit venom-lecithin hemolysis, but unheated turtle serum may have a slight 

 inhibiting action. The turtle serum contains perhaps both activating and 

 inhibiting substances; in some cases the activating, in other cases the inhibit- 

 ing substance prevailing. 



IX. The corpuscles of a rabbit immunized against heloderma venom were 

 hemolyzed by venom and lecithin as well as by venom and an activating serum; 

 its corpuscles were, however, somewhat more resistant than those of a control 

 rabbit. The serum of a rabbit immunized against heloderma venom does not 

 activate the venom, but inhibits venom-lecithin hemolysis in the same manner 

 as normal rabbit serum. 



X. The hemolysins of the venom of Heloderma resist heating to 100 C. for 

 10 minutes. After heating to 100 C. for 30 minutes the hemolytic power of 

 heloderma venom is markedly injured and usually destroyed; after heating to 

 120 C. for 15 minutes (in the autoclave) the hemolysins are completely de- 

 troy ed. The heat resistance of the hemolytic substances of heloderma venom 

 is therefore similar to the heat resistance of certain snake venoms and inferior 

 to the heat resistance of the neurotoxic property of the heloderma venom. 



XI. The addition of a small amount of acid to the normally neutral venom 

 solution does not change its hemolytic properties. 



XII. The venom of Heloderma suspectum and Heloderma horridum act in 

 the same manner, both being activated by lecithin, or horse or clog serum, and 

 neither possessing the power to hemolyze red blood-corpuscles unless these 

 activating substances are added. They are also equally heat resistant. 



XIII. The hemolysins of the heloderma venom differ in certain respects 

 from hemolysins of snake venoms, since they can not be activated by "com- 

 plements" (such as are contained in guinea-pig serum). It may also be added 

 that, compared with such powerful hemolytic agents as the cobra venom, the 

 venom of Heloderma is only weakly hemolytic. 



