440 DISEASES DUE TO J'ENOMS AND POISONS 



(4) .Vnlihccmolysins. 



(5) Antibacterial substances. 



(6) A fibrin ferment. 



(7) An a mi fibrin ferment. 



(8) A proteolytic ferment. 



(9) A cardiac tonic. 



Xiniibers (i), (3) and (()) are the most important. 

 Xo one snake yields all these varieties of venom. 



To analyse Snake Yenom (Martin). 



(i) Dialysing and filtering it through a gelatine filter, supported 

 in the pores of a Pasteur-Chamberland filter. Fibrin ferments and 

 hsemorrhagins do not dialyse. 



(2) Heat from 70° to 100° C. Some neurotoxins and hc'emolysins 

 will not be affected. 



(3) Digest ^\ilh red blood cells and serum, previously heated to 

 50° C. The hcemol}sins are thus separated from the neurotoxins. 

 The erythrocytes remove the h^emohsins ; the heating removes the 

 hasmorrhagin, so that the neurotoxin alone remains. 



Neurotoxins are very important. The venom of the Colubrinae 

 contains much. It unites with the nerve cells, attacks the respiratory 

 centre in the medulla,, reducing the. respirations in number and 

 amplitude to cessation, and paralyses the jDhrenic end plates in the 

 diaphragm. The circulation ma\' be kept going for some time after 

 ces.sation of breathing if artificial respiration be resorted to. 



The venom of some snakes, however, sucii as A'iper russelli, Bitis 

 arietans. Crotalus horridus, and Lachechis anamallensis, contains a 

 neurotoxin that acts upon the vasomotor centre of the medulla affecting 

 the blood-pressure. When the nerve cells are attacked the Nissl 

 granules break up into a fine dust-like deposit, the nucleus remains 

 central but indistinct. In sudden death no change is noted. The cells 

 are, as a rule, unequally effected. 



Agglutinins. — These are destroyed by heating to 75°-8o° C. White 

 and red cells may be agglutinated. To see this reaction, add a 10 per 

 cent, solution of dried venom in normal saline to washed corpuscles 

 suspended in normal saline. The cellular outline mav be modified. 



Cytolysins are of four groups : — 



Hasmolysins. — A 2 per cent, solution of the \'iper berus venom 

 and a o*i per cent, solution of Pseudechis venom destrovs red cells in 

 eighteen to twenty-four hours. These also remove the antibactericidal 

 properties of the blood in most instances, but not in the case of the 

 Necturus. The .same venom that acts upon human red cells mav not 

 act upon those of other animals; this feature depends solelv upon the 



