Pasteur went on to Arbois from Copenhagen. The laboratory he had built there not being large enough to take in rabid dogs, he dictated from his study the experiments to be carried out in Paris; his carefully kept notebooks enabled him to know exactly how things were going on. His nephew, Adrien Loir, now a curator in the laboratory of Rue d’Ulm, had gladly given up his holidays and remained in Paris with the faithful Eugène Viala. This excellent assistant had come to Paris from Alais in 1871, at the request of Pasteur, who knew his family. Viala was then only twelve years old and could barely read and write. Pasteur sent him to an evening school and himself helped him with his studies; the boy was very intelligent and willing to learn. He became most useful to Pasteur, who, in 1885, was glad to let him undertake a great deal of the laboratory work, under the guidance of M. Roux; he was ultimately entrusted with all the trephining operations on dogs, rabbits, and guinea-pigs.
The letters written to him by Pasteur in 1884 show the exact point reached at that moment by the investigations on hydrophobia. Many people already thought those studies advanced enough to allow the method of treatment to be applied to man.
Pasteur wrote to Viala on September 19, “Tell M. Adrien (Loir) to send the following telegram: ‘Surgeon Symonds, Oxford, England. Operation on man still impossible. No possibility at present of sending attenuated virus.’ See MM. Bourrel and Béraud, procure a dog which has died of street-rabies, and use its medulla to inoculate a new monkey, two guinea-pigs and two rabbits.... I am afraid Nocard’s dog cannot have been rabid; even if you were sure that he was, you had better try those tests again.
“Since M. Bourrel says he has several mad dogs at present, you might take two couple of new dogs to his kennels; when he has a good biting dog, he can have a pair of our dogs bitten, after which you will treat one of them so as to make him refractory (carefully taking note of the time elapsed between the bites and the beginning of the treatment). Mind you keep notes of every new experiment undertaken, and write to me every other day at least.”
Pasteur pondered on the means of extinguishing hydrophobia or of merely diminishing its frequency. Could dogs be vaccinated? There are 100,000 dogs in Paris, about 2,500,000 more in the provinces: vaccination necessitates several preventive inoculations; innumerable kennels would have to be built for the purpose, to say nothing of the expense of keeping the dogs and of providing a trained staff capable of performing the difficult and dangerous operations. And, as M. Nocard truly remarked, where were rabbits to be found in sufficient number for the vaccine emulsions?
Optional vaccination did not seem more practicable; it could only be worked on a very restricted scale and was therefore of very little use in a general way.
The main question was the possibility of preventing hydrophobia from occurring in a human being, previously bitten by a rabid dog.
The Emperor of Brazil, who took the greatest interest in the doings of the Ecole Normale laboratory, having written to Pasteur asking when the preventive treatment could be applied to man, Pasteur answered as follows—
“September 22.
“Sire—Baron Itajuba, the Minister for Brazil, has handed me the letter which Your Majesty has done me the honour of writing on August 21. The Academy welcomed with unanimous sympathy your tribute to the memory of our illustrious colleague, M. Dumas; it will listen with similar pleasure to the words of regret which you desire me to express on the subject of M. Wurtz’s premature death.