INTRODUCTION. 7 



the blood-cells of Limidus. I found many analog;ies between the action of 

 these factors on colloitls of a proteid character and on the living cells. 



The venoms of snakes, as far as they have been investigated in this respect, 

 do not only possess the power to hemolyze erj'throcytes, but also other kinds of 

 cells, cspeciallj- leucocytes. In contradistinction to snake venom, venom of 

 Heloderma does not possess this d('structi\e jjower. No dissolving or agglu- 

 tinating effect upon leucocytes is noticeable, which maj' even show great 

 phagocytic power, notwithstanding the presence of venom (Tuttle). After 

 addition of heloderma venom phagocytosis takes place in riro as well as in 

 vitro and apparently in undiminished strength. 



After a_subcutaneous injection of heloderma venom a marked increase in 

 the number of polynuclear leucocytes takes place in the peripheral circulation. 

 This reaction was cspecialh' marked in animals during the process of immu- 

 nization, where relatively large quantities of venom could be administered. 

 How far this reaction depends merelj' upon differences in distribution of leu- 

 cocytes, or on an actual increase in the output of polynuclear leucocytes into 

 the blood-vessels from the bone-marrow, has to be decided by further investi- 

 gation (M. K. Meyers and Lucius Tuttle). 



As previously stated, the heloderma venom liagjiadixeet hemolytic effect ; 

 it does not digest muscle, it does not destroy leucocytes, and, we may add, it 

 lias no noticeable effect upon eggs of Echinoderms. 



Cobra venom and other snake venoms have a very decided lytic effect 

 upon various kinds of cells; they even are able to destroy bacteria. In this 

 respect heloderma and cobra venom differ \'ery markedl}-, while in the manner 

 in which both venoms affect the living animal organism there exists much 

 similarity; both are principally neurotoxic, causing lesions in nerve-cells and 

 exerting their lethal effect by paralysis of the respiratory center. 



The similarity between certain snake venoms and the venom of Heloderma 

 is also apparent in the parallelism that exists between the doses lethal for vari- 

 ous species. Against the venom of Heloderma as well as of Cobra, Bungarus 

 coeruleus, Enhydrina valakadien it is found that the white rat is relatively more 

 resistant than most of the other mammals tested, but this increase in resist- 

 ance does not extend to all the snake venoms. Thus, according to Fraser 

 and Gunn (Phil. Transactions Roj'. Soc, t. 202), the white rat is even more 

 susceptible to the venom of Echis carinatus, which resembles in its action 

 crotalus venom, than the rabbit or the guinea-pig. A further similarity is 

 the following: cold-blooded verteb rates are more resistant toward cobrg, and 

 certain other snake venoms, as well as against heloderma venom, than are 

 the warm-blooded animals. Certain differences, however, exist among cold- 

 blooded animals in regard to their susceptibilitj' toward heloderma venom. 

 Especially is this true of Joads , which show a marked degree of resistanc^e. 

 During different stages of development, the susceptibility toward heloderma 

 venom may vary. Tadpoles are undoubtedly more susceptible to heloderma 

 venom than adult frogs. ^Jl_the_jnwrtebrates which we tested were immune 

 against the action of venom, while Fundidiis, a salt-water fish, was susceptible. 



