THE VENOM 



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in the centre of the cell. The cells are unequally attacked. Those 

 around the central canal are most severely injured, Avhile the 

 motor cells are little affected. In sudden death no change is noted. 

 He says that the character of the changes are of the same order 

 as those described by Marinesco as toxic degeneration, and are 

 very like those following the fatal dose of abrin. Inflammatory 

 and vascular changes are absent. 



As to the cause of this cytolysis, it would appear from the re- 

 searches of Flexner and Noguchi that it is probably due to the 

 union of an endocomplement (capable of being neutralized by 

 calcium chloride, and therefore not lecithin) in the nerve cell with 

 an amboceptor in the venom. This neurotoxin, according to 

 Ehrlich's denomination, is neurotropic — i.e., unites only with nerve 

 cells — and monotropic — -i.e., has affinities for one tissue only. 



These facts have been demonstrated by Flexner and Noguchi in 

 cobra-venom by first treating it with erythrocytes to remove the 

 hsemolysin, and then heating it to destroy the haemorrhagin, thus 

 leaving only the neurotoxic principle to act on the animal. 



They found that after cerebral injection the appearance of the 

 nervous symptoms was almost immediate, while with other methods 

 of injection the development was more gradual. 



The first effect of the neurotoxin was irritation (convulsions), 

 and the final paralysis. By cobra-venom, death was caused by 

 respiratory paralysis. Intracerebral injection of a viperine venom 

 like that of Crotalus, however, caused but slight symptoms. 



They further found that the venoms of Ancistrodon piscivorus 

 Lacep. and A. contortrix L. occupied an intermediate position 

 between the colubrine and viperine venoms, containing both neuro- 

 toxins and haemolysins in considerable quantities. From these 

 experiments it was possible to classify venoms into the three classes 

 given above. 



2. Agglutinins. — -Agglutination of the red cells was first de- 

 scribed by Weir Mitchell and Reichert, and that of the leucocytes 

 by Halford and Ralf. 



The reaction can be studied by adding a o-oi per cent, to 10 per 

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

 suspended in normal saline. 



The time required for agglutination depends upon the strength 

 of the solution of venom, and the effect upon the corpuscles depends 

 upon whether they come together quickly or slowly. In the former 

 case they are not damaged, while in the latter their shape is con- 

 siderably altered. Agglutinins are destroyed by heating the venom 

 to 75°-8o° C. _ 



The agglutinins for the red cells appear to be the same sub- 

 stances as those for the white, and in both cases they appear to 

 act prior to the cytolysis of the cells. 



3. The Cytolysins. — {a) Hcemolysins. — Fontana many years ago 

 noted that the blood of animals bitten by vipers was fluid, and Weir 

 Mitchell and Reichert described the haemoglobin dissolving out of 



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