454 



MANUAL OF ZOOLOGY 



(Fig. 272, Mc), one of the muscles which raise the lower 

 jaw: it is thus forced along the duct (Gc) to the aperture 

 (za), and injected into the wound made by the fang. The 

 effect is to produce acute pain with increasing lethargy and 

 weakness, and in the case of the venom of some kinds of 

 snakes, paralysis. According to the relative amount of the 

 poison injected and the degree of its virulence (which differs 

 not only in different kinds of snakes, but in the same snake 

 under different conditions) the symptoms may result in 

 death, or the bitten animal may recover. The poison is a 



Me ?. Km 



Fig. 272. — Poison apparatus of rattlesnake. A, eye; Gc, poison-duct entering 

 the poison-fang at f ; Ktn, muscles of mastication partly cut through at * ; jl/c, 

 masseter or constrictor muscle; Mc' , continuation of the constrictor muscle to the 

 lower jaw ; iV, nasal opening ; .S", fibrous poison-sac ; z, tongue ; za, opening of 

 the poison-duct ; zf, pouch of mucous membrane enclosing the poison-fangs. 

 (FromWiedersheim. ) 



clear, slightly straw-coloured or greenish liquid ; it preserves 

 its venomous properties for an indefinite period, even if 

 completely desiccated. The poisonous principles are cer- 

 tain proteids not to be distinguished chemically from other 

 proteids which have no such poisonous properties. Immu- 

 nity against the effects of the poison, and relief of the symp- 

 toms after a bite has been inflicted, have been found to be 

 conferred by injections of the serum of animals which have 



