Pasteur's study of rabies began in 1880; and the date of the first case treated--Joseph Meister, a shepherd-boy of Alsace--is July 1885. The first part of the work was spent in a prolonged search for the specific microbe of rabies. It was not found: its existence is a matter of inference, but not of observation.[24] In his earlier inoculations, Pasteur made use of the saliva of rabid animals; and M. Valléry-Radot tells the story, how Pasteur took him on one of his expeditions:-- "The rabid beast was in this case a huge bull-dog, foaming at the mouth and howling in his cage. All attempts to induce the animal to bite, and so infect one of the rabbits, failed. 'But we _must_,' said Pasteur, 'inoculate the rabbits with the saliva.' Accordingly a noose was made and thrown, the dog secured and dragged to the edge of the cage, and his jaws tied together. Choking with rage, the eyes bloodshot, and the body convulsed by a violent spasm, the animal was stretched on a table, and kept motionless, while Pasteur, leaning over his foaming head, sucked up into a narrow glass tube some drops of the saliva." [24] This sentence was written before the publication of Professor Negri's observations (see _Medical Annual_, 1906, p. 418). But these inoculations of saliva sometimes failed to produce the disease; and, when they succeeded, the incubation-period was wholly uncertain: it might be some months before the disease appeared. Thus Pasteur was led to use, instead of the saliva, an emulsion of the brain or spinal cord; because, as Dr. Duboué had suggested, the central nervous system is the chief seat, the _locus electionis_, of the virus of rabies. But these inoculations also were not always successful, nor did they give a definite incubation-period. Therefore he followed with rabies the method that he had followed with anthrax. As he had cultivated the virus of anthrax, by putting it where its development could be watched and controlled, so he must put the virus of rabies in the place of its choice. It has a selective action on the cells of the central nervous system, a sort of affinity with them; they are, as it were, the natural home of rabies, the proper nutrient medium for the virus: therefore the virus must be inoculated not under the skin, but under the skull. These sub-dural inoculations were the turning-point of Pasteur's discovery. The first inoculation was made by M. Roux:-- "Next day, when I informed Pasteur that the intracranial inoculation offered no difficulty, he was moved with pity for the dog. 'Poor beast, his brain is doubtless injured: he must be paralysed.' Without reply I went down to the basement to fetch it, and let it come into the laboratory. Pasteur did not like dogs, but when he saw this one, full of life, inquisitively rummaging about in all directions, he exhibited the greatest delight, and lavished most charming words upon it."