122 OPHIDIANS. 
Saliva is a secretion of rapid formation, and appropriated 
to specific mechanical and chemical purposes within the 
economy ; the venom-fluid is slowly elaborated, slowly re- 
_produced when lost, and destined to end in the body which 
produces it. 
Its singular nature as a ferment, poisonous to other animals 
as well as to the reptile in which it is secreted, constitutes a 
distinction which forbids the physiologist to regard it as in 
any true sense a salivary secretion, or its forming organ as a 
salivary gland. Extensive experiments with chemical re- 
agents, as well as with extremes of heat and cold, have un- 
folded the singular energy of this poison, and the almost 
inconceivable tenacity with which its powers are preserved. 
The dried venom retained its potency after two years of 
climatic changes; the fresh poison, although prone to partial 
decomposition, would remain active after a sojourn of several 
weeks in an atmosphere of 65° to 70° Fahrenheit. 
Mixing the venom with water, and freezing it, and keeping 
it for half an hour at 4° above zero, did not in the least 
diminish its power; nor did a temperature of 212° Fahr. de- 
stroy its virulence. 
In eight experiments Dr. Mitchell has shown that: 
1. The coagulum produced by heat is always innocent. 
2. The supernatant fluid is uniformly poisonous. The 
cases died with the usual rapidity. A fact which leads us to 
infer that the venom loses no power by being heated to a 
certain degree. 
The animals which perished from the injection of the boiled 
venom exhibited very trifling local evidences of the action of 
the poison. Dr. Mitchell is unable to offer any plausible 
explanation of this curious deficiency. (Were he a believer 
in the dynamic origin of disease and the action of remedies, 
he would be better able to comprehend this phenomenon.) 
