The activity of the poison of the viper depends on a variety of circumstances. When kept long confined, the animal loses its energy; and after it has bitten repeatedly in rapid succession, its bite ceases for some time to be poisonous, as the supply of poison is exhausted. It appears also to be most active in hot and dry climates. Those cases are always the most severe in which the symptoms begin soonest; and the danger increases with the number of bites. An important observation made by Dr. Wagner is that danger need not be dreaded except when the bite is inflicted on small organs such as the fingers or toes, because larger parts cannot be fully included between the animal's jaws, and fairly pierced by its fangs, but can only be scratched. The properties of the fluid contained in the reservoir do not cease with the animal's life; nay they continue even when the fluid is dried and preserved for a length of time. It may be swallowed in considerable quantity without causing any injury whatever. In the course of some experiments lately made in Italy, a pupil of Professor Mangili swallowed at once the whole poison of four vipers without suffering any inconvenience; and that of six vipers was given to a blackbird, that of ten to a pigeon, and that of sixteen to a raven, with no other effect beyond slight and transient stupor.[1]
For the most recent account of the far more terrible effects of the cobra di capello and rattlesnake, the reader may refer to the authorities below.[2]
It was stated above that the poison of the viper retains its activity when dried. I have had an opportunity of observing this in regard to the poison of the cobra di capello, which is said to be preserved in India by simply squeezing out the contents of the poison-bag, and drying the liquid in a silver dish exposed to the sun. The specimen in my possession, for which I am indebted to Mr. Wardrop of London, has the appearance of small fragments of gum-arabic. It had been kept for fifteen years when I tried its effects on a strong rabbit. A grain and a half dissolved in ten drops of water, having been introduced between the skin and muscles of the back, the animal in eight minutes became very feeble and averse to stir, so that it remained still even when placed in irksome postures; occasional slight twitches of the limbs supervened; at length it became extremely torpid, and breathed slowly by means of the abdominal muscles and diaphragm alone; and in twenty-seven minutes it died exhausted, without any precursory insensibility. The heart contracted readily, when irritated nine minutes after death; so that the poison seemed to operate by causing muscular paralysis, and consequently arresting the respiration.
There might also be arranged in an appendix to the present group of poisons those insects whose sting is poisonous. The European insects known to have a poisonous sting, are chiefly the scorpion, tarantula, bee and wasp; of which the last two only are natives of Britain.
