Sometimes these substances are simply discharged into the surrounding medium, and serve to keep off enemies (_toad_, _salamander_); sometimes they mingle with the fluids and digestive juices, and then play an important part in the nourishment of the animal that produces them (_snakes_); in other cases, again, they are capable of being inoculated by means of _stings_ or _teeth_ specially adapted for this purpose, and then they serve at once as a means of attack or defence, and as a digestive ferment (_snakes_, _spiders_, _scorpions_, _bees_). An animal is said to be _venomous_ when it possesses the power of _inoculating_ its venom. Venomous species are met with in almost all the lower zoological groups, in the _Protozoa_, _Cœlenterates_, _Arthropods_, _Molluscs_, and in a large number of _Vertebrates_ (fishes, amphibians, and reptiles). The _reptiles_ are best endowed in this respect, and it is in this class of creatures that we meet with the species most dangerous to man and to mammals in general. The study of their venom, too, is of considerable interest, since it should lead to the quest of means of protection sufficiently efficacious to preserve us from their attacks. * * * * * Venomous reptiles are not always easy to distinguish from those devoid of any inoculatory apparatus. For this reason both classes alike have at all times inspired mankind with a lively dread, which is displayed among the various races in legends and religious beliefs. In ancient days the cult of the snake occupied a prominent place. In _Genesis_ the serpent is the incarnation of the Evil One, tempting and deceitful. In Greece it was the symbol of wisdom and prudence. In Egypt it was associated with the Sacred Scarabæus and the flowers of the lotus to represent Immortality! At Rome epidemics ceased when the snake sacred to Æsculapius was brought from Epidaurus. According to Kraff, the Gallas of Central Africa consider the snake as the ancestor of the human race, and hold it in great respect. In India the cult of the Seven-headed _Naja_, or serpent-god, was formerly almost as flourishing as that of Buddha. It is still regarded as a crime to kill a Cobra when it enters a hut; prayers are addressed and food is offered to it. Its presence is an omen of happiness and prosperity; it is believed that its death would bring down the most terrible calamities on whomsoever should have brought it about, and on his family. Nevertheless, in the Indian Peninsula alone, the Cobra, the Krait, and a few other extremely poisonous species of snakes cause every year an average of _25,000_ deaths. The number of fatalities from the same cause is likewise considerable in Burma, Indo-China, the Dutch Indies, Australia, Africa, the West Indies and Tropical America generally. The temperate regions of the globe are less severely affected; North America the Rattle-snake and the Moccasin are especially deadly.