One or two days before the third and decisive inoculation, the veterinary surgeon of Pont-sur-Yonne, M. Biot, who was watching with a rare scepticism the Pouilly le Fort experiments, met Colin on the road to Maisons-Alfort. “Our conversation”—M. Biot dictated the relation of this episode to M. Thierry, his colleague, also very sceptical and expecting the Tarpeian Rock—“our conversation naturally turned on Pasteur’s experiments. Colin said: ‘You must beware, for there are two parts in the bacteridia-culture broth: one upper part which is inert, and one deep part very active, in which the bacteridia become accumulated, having dropped to the bottom because of their weight. The vaccinated sheep will be inoculated with the upper part of the liquid, whilst the others will be inoculated with the bottom liquid, which will kill them.’” Colin advised M. Biot to seize at the last moment the phial containing the virulent liquid and to shake it violently, “so as to produce a perfect mixture rendering the whole uniformly virulent.”
If Bouley had heard such a thing, he would have lost his temper, or he would have laughed heartily. A year before this, in a letter to M. Thierry, who not only defended but extolled Colin, Bouley had written:
“No doubt Colin is a man of some value, and he has cleverly taken advantage of his position of Chief of the Anatomy department at Alfort to accomplish some important labours. But it is notable that his negative genius has ever led him to try and demolish really great work. He denied Davaine, Marey, Claude Bernard, Chauveau; now he is going for Pasteur.” Bouley, to whom Colin was indebted for his situation at Alfort, might have added, “And he calls me his persecutor!” But Biot refused to believe in Colin’s hostility and only credited him with scruples on the question of experimental physiology. Colin did not doubt M. Pasteur’s bona fides, M. Biot said, but only his aptitude to conduct experiments in anima vili.
On May 31, every one was at the farm. M. Biot executed Colin’s indications and shook the virulent tube with real veterinary energy. He did more: still acting on advice from Colin, who had told him that the effective virulence was in direct proportion to the quantity injected, he asked that a larger quantity of liquid than had been intended should be inoculated into the animals. A triple dose was given. Other veterinary surgeons desired that the virulent liquid should be inoculated alternatively into vaccinated and unvaccinated animals. Pasteur lent himself to these divers requests with impassive indifference and without seeking for their motives.
At half-past three everything was done, and a rendezvous fixed for June 2 at the same place. The proportion between believers and unbelievers was changing. Pasteur seemed so sure of his ground that many were saying “He can surely not be mistaken.” One little group had that very morning drunk to a fiasco. But, whether from a sly desire to witness a failure, or from a generous wish to be present at the great scientific victory, every man impatiently counted the hours of the two following days.
On June 4, Messrs. Chamberland and Roux went back to Pouilly le Fort to judge of the condition of the patients. Amongst the lot of unvaccinated sheep, several were standing apart with drooping heads, refusing their food. A few of the vaccinated subjects showed an increase of temperature; one of them even had 40° C. (104° Fahrenheit); one sheep presented a slight œdema of which the point of inoculation was the centre; one lamb was lame, another manifestly feverish, but all, save one, had preserved their appetite. All the unvaccinated sheep were getting worse and worse. “In all of them” noted M. Rossignol, “breathlessness is at its maximum; the heaving of the sides is now and then interrupted by groans. If the most sick are forced to get up and walk, it is with great difficulty that they advance a few steps, their limbs being so weak and vacillating.” Three had died by the time M. Rossignol left Pouilly le Fort. “Everything leads me to believe,” he wrote, “that a great number of sheep will succumb during the night.”
Pasteur’s anxiety was great when Messrs. Chamberland and Roux returned, having noticed a rise in the temperature of certain vaccinated subjects. It was increased by the arrival of a telegram from M. Rossignol announcing that he considered one sheep as lost. By a sudden reaction, Pasteur, who had drawn up such a bold programme, leaving no margin for the unexpected, and who the day before seemed of an imperturbable tranquillity among all those sheep, the life or death of whom was about to decide between an immortal discovery and an irremediable failure, now felt himself beset with doubts and anguish.
Bouley, who had that evening come to see his master, as he liked to call him, could not understand this reaction—the result of too much strain on the mind, said M. Roux, whom it did not astonish. Pasteur’s emotional nature, strangely allied to his fighting temperament, was mastering him. “His faith staggered for a time,” writes M. Roux, “as if the experimental method could betray him.” The night was a sleepless one.
“This morning, at eight o’clock,” wrote Mme. Pasteur to her daughter, “we were still very much excited and awaiting the telegram which might announce some disaster. Your father would not let his mind be distracted from his anxiety. At nine o’clock the laboratory was informed, and the telegram handed to me five minutes later. I had a moment’s emotion, which made me pass through all the colours of the rainbow. Yesterday, a considerable rise of temperature had been noticed with terror in one of the sheep; this morning that same sheep was well again.”
On the arrival of the telegram Pasteur’s face lighted up; his joy was deep, and he desired to share it immediately with his absent children. Before starting for Melun, he wrote them this letter: