Impatient with the length of time required for the incubation of the disease, and with the obligation of waiting whole months for the result of an experiment, when the subject demanded such numerous ones, Pasteur began to seek some means of producing hydrophobia with certainty and of making it appear more rapidly. Notwithstanding the assertion of a professor of the veterinary school at Lyons that the saliva of the rabid dog alone contained the virus of the disease, and that he had failed in every attempt to inoculate, whether with the substance of the brain or with the spinal marrow of rabid dogs; Pasteur, with due care as to purity, introduced under the skin of some rabbits and some dogs, divers parts of the brain of a dog which had died in a rabid state. Hydrophobia declared itself in both dogs and rabbits, with a duration of incubation about equal to that which followed the ordinary bite of a dog. Although it was necessary still to submit to this long uncertainty with regard to the incubation, one great result was obtained: hydrophobia _could_ be inoculated with other matter than saliva. Not only is the saliva always impure, containing a saliva microbe, which is endowed with a special virulence of its own, but it presents other inconveniences. It is necessary, in these researches, to have a supply of material constantly at hand. Now, the saliva loses its rabic virulence in twenty-four hours. The existence of the rabic virulence in the brain substance placed, on the contrary, at the disposal of the experimenter, an abundance of the virus, in a state of great purity and capable of long preservation. * * * * *