Chemistry has made astounding strides since the days of the sixteenth century, when Italian malice and intrigue swayed all Europe, and poisons and poisoners stalked forth unblushingly from cottage and palace; when crowned and mitered heads, prelates, noblemen, beneficed clergymen, courtiers, and burghers became Borgias and De Medicis in hideous infamy in their greed for power and affluence; and when the civilized world feared to retire to rest, partake of the daily repast, inhale the odors of flower or perfume, light a wax taper, or even approach the waters of the holy font. These horrors have been laid bare, their cause and effect explained, and tests discovered whereby they may be detected, providing the law with a shield that protects even the humblest individual. Great as the science is, however, it is yet far removed from perfection; and there are substances so mysterious, subtle, and dangerous as to set the most delicate tests and powerful lenses at naught, while carrying death most horrible in their train; and chief of these are the products of Nature's laboratory, that provides some sixty species of serpents with their deadly venom, enabling them in spite of sluggish forms and retiring habits to secure abundant prey and resent mischievous molestation. The hideous _trigonocephalus_ has forced the introduction and acclimation of the mongoose to the cane fields of the Western tropics; the tiger snake (_Heplocephalus curtus_) is the terror of Australian plains; the fer de lance (_Craspedocephalus lanceolatus_) renders the paradise of Martinique almost uninhabitable; the tic paloonga (_Daboii russelli_) is the scourge of Cinghalese coffee estates; the giant ehlouhlo of Natal (unclassified) by its presence secures a forbidding waste for miles about; the far famed cobra de capello (_Naja tripudians_) ravages British India in a death ratio of one-seventh of one per cent. of the dense population, annually, and is the more dangerous in that an assumed sacred character secures it largely from molestation and retributive justice; and in Europe and America we have vipers, rattlesnakes, copperheads, and moccasins (_viperinæ_ and _crotalidæ_), that if a less degree fatal, are still a source of dread and annoyance. All these forms exhibit in general like ways and like habits, and if the venom of all be not generically identical, the physiological and toxicological phenomena arising therefrom render them practically and specifically so. Indeed, their attributes appear to be mere modifications arising from difference in age, size, development, climate, latitude, seasons, and enforced habits, aided perhaps by idiosyncrasies and the incidents and accidents of life.