The rapidity with which it acts is also extremely remarkable. Thus, if a rabbit receive two cubic centimetres (about fifty drops) of anti-venomous serum in the marginal vein of one of its ears, it will suffer with absolute impunity an injection of venom into the marginal vein of the other ear capable of killing it under ordinary circumstances in a quarter of an hour. Its curative powers are not less remarkable, for it is possible to inject venom sufficient to kill an animal in two hours, and to let one hour and three-quarters elapse before administering the antidote, and yet at this late stage to save the victim's life, although it is necessary where such a long interval has occurred between the respective venom and serum injections to employ the latter in larger quantities than is usually required. Dr. Calmette believes that the anti-toxin may be applied at an even more advanced stage of the disease if it is employed in yet larger doses. Another novel and important feature about this anti-venomous serum is the fact that it not only protects animals from one species of very active venom, such as that of the cobra and other poisonous snakes, but it also affords protection from the dreaded venom of scorpions. This is a very remarkable and significant discovery, for hitherto the opinion has been stubbornly held that each toxin requires its specific anti-toxin for its correction. Dr. Calmette has, however, frequently indicated by his researches that this view cannot be considered so completely proven as is claimed by its supporters, and his latest investigations support the theory that particular toxins may be counteracted by several anti-toxins of different origin. Thus it has been shown by Calmette and Roux that rabbits hyper-vaccinated against rabies acquire the power of resisting venom-poison, and that the serum of horses vaccinated against tetanus or lock-jaw also nullifies the action of serpent venom. The practical bearing of this discovery is obvious, and the hope is justified that the at present cumbrous appliances required for the elaboration of anti-toxins of such varied origin will ultimately give way to simpler and less costly methods, which will admit of these new antidotes being more widely circulated and applied. We have seen that although most animals fall an easy prey to serpent venom, yet there are a few notable exceptions, amongst which may be mentioned hedgehogs, swine, and the mongoose. Now the very natural question arises why, if these animals are already in such a high degree immune from this poison, should not they be employed to furnish forth protective serum, instead of laboriously training up susceptible animals to become artificially immune and supply this venom anti-toxin?