INTRODUCTION. 637 
into the base of the fang, contract, drawing the point of the latter back- 
ward, thus deepening the wound, and in part forcing out the venom. 
This is followed by still another motion or rather two other movements, 
a rolling outward of the two upper maxillary bones and with them 
the fangs, so that if the animal misses its aim it may not bite itself, and 
the closure of the mouth. The latter is effected by various muscles, 
among which the anterior temporal lies over the posterior two-thirds of 
the poison sac, and in contracting, forcibly compresses the glands and 
compels the venom to flow out through the duct and tooth into the 
wound. That the duct does not enter the tooth is true, but the sheath 
falling at the base completes the channel, though in rare cases not per- 
fectly, but permits the fluid to escape alongside the fang. After having 
thus struck its victim, deepened the wound, and injected a sufficient 
quantity of venom, the animal opens its mouth and lets go its hold. 
Occasionally it happens that the teeth of the lower jaws become en- 
tangled, and the serpent is unable to get away. It will then shake its 
head from side to side, not as is ordinarily supposed on account of rage, 
but in its efforts to escape. At times, also, only one of the fangs pene- 
trates the wound, and the victim receives only half the usual amount of 
venom. In such a case, or in case the venom was spilled outside the fang, 
or the serpent’s supply was exhausted by its having previously bitten 
an enemy, a physician might be seriously misled as to the effects of a 
remedy. 
In structure, as Prof. Owen* has shown, the fang may be likened unto 
a simple tooth, flattened and then turned up so as to bring the edges 
together, thus forming a cylinder or rather a cone open at both ends. 
The suture is along the anterior or convex side of the tooth, thus bring- 
ing the veniferous canal in front of the puip cavity. The venom is 
secreted by the glands, and the only cavities for its storage are the ducts, 
hence the terms poison sacs, vesicles, etc., are misnomers, and ought be 
abolished. 
The average amount of venom thrown out at once by a serpent, three 
or four feet long, is from two to four drops, though in some cases as mueh 
as fifteen drops has been given off through a single fang. By filling the 
glands with water their capacity has been estimated at from eleven to 
twenty-nine drops. The color of the venom varies from pale green to 
orange ; its specific gravity is from 10.30 to 10.44 ; it is tasteless, acid, dries 
slowly, and is then adhesive, and its virulence is not affected by heat or 
cold. Heat, however, produces an albuminous precipitate which is harm- 
*Comp. Anatomy, Vol. I, p. 396. 
