1464 HYGIENE 



duration of the eventual captivity of the snake. The largest quantity can 

 be obtained from the king cobra and the smallest from some species of Hy- 

 dropinae. From a cobra iNaja Haje) 200 mgms. of dried venom, correspond- 

 ing with 670 mgms. of the fresh substance, have been obtained in the 

 course of an experiment which lasted four months. 



The principal physical characteristics of the venoms, which vary 

 greatly according to the species ; colour, taste, state after drying, and solu- 

 bihty, are described. The general action of venoms is then considered, 

 and after a recapitulation of the different researches on the question, the 

 conckision is drawn that these products are very complex lif|uids contain- 

 ing some of the following constituents, aU of them not being present in 

 orvery venom. 



r) Neurotoxins. 



a) Acting principally on the respiratory centre. 



h) Acting principally on the vaso- rotator}^ centre. 



c) Acting principally on the nerves and the discs of the fibres of the 

 striated muscles, particularly of phrenic muscles. 



2) Agglutins. 



3) Cytolysins. 



a) Haemotysins. 



b) Leucolysins. 



c) Haemorrhagins. 



4) A fibrin enzyme. 



5) A -proteolytic enzyme. 



6) Antibactericide substances. 



The neurotoxins constitute the most active principles of most venoms. 



The effects of the bite of venomous snakes are then described . The 

 neurotoxins, which have an affinity for the respiratory centres, predomi- 

 nate in the venom of the Colubridae. This class, of which with regard to 

 the action of the venom, Naja tripudians is typical, produces general pa 

 ralysis with a specific paralysis of the respiratory mechanism. In the ve- 

 nom of the Viperidae the toxins acting on the blood and circulatory system 

 predominate ; this venom, particularly that of Vipera russellii, acts on 

 the blood and circulatory sj'stem producing a sudden appearance of various 

 symptoms, with a tendency to an extension of the gangrenous destruction 

 from the local lesion, if the animal survives the acute stage. 



The first scientific attempt to immunise against snake venom was made 

 in 1887, Sewaix having then immimised pigeons by small repeated doses, 

 so that they were afterwards able to withstand ten times the fatal dose of 

 Crotalus venom In 1892 Ca.lmette employed venom heated at 80" C to 

 immunioe rabbits, but his serum, being originally from Colubridae, had but 

 little action for the Viperidae. Pure specific sera have since been prepared 

 by others, for example : 



Lamb's serum, derived from Naja tripudians (strongly antitoxic 

 against cobra venom). 



I,amb's serum, derived from Vipera russellii (anti-toxic against Vipe- 

 rinae venom). 



