The life of Pasteur

by René Vallery-Radot

Nisard answered on May 7: “My very dear friend, I am almost dazed with the effort made by my ignorance to follow your ideas, and dazzled with the beauty of your discoveries on the principal point, and the number of secondary discoveries enumerated in your marvellous paper. You are right not to care for barren praise; but you would wrong those who love you if you found no pleasure in being praised by them when they have no other means of acknowledging your notes.

“I am reading the notice on chicken-cholera for the second time, and I observe that the writer is following the discoverer, and that your language becomes elevated, supple and coloured, in order to express the various aspects of the subject.

“It gives me pleasure to see the daily growth of your fame, and I am indeed proud of enjoying your friendship.”

Amidst his researches on a vaccine for chicken-cholera, the etiology of splenic fever was unceasingly preoccupying Pasteur. Did the splenic germs return to the surface of the soil, and how? One day, in one of his habitual excursions with Messrs. Roux and Chamberland to the farm of St. Germain, near Chartres, he suddenly perceived an answer to that enigma. In a field recently harvested, he noticed a place where the colour of the soil differed a little from the neighbouring earth. He questioned M. Maunoury, the proprietor of the farm, who answered that sheep dead of anthrax had been buried there the preceding year. Pasteur drew nearer, and was interested by the mass of little earth cylinders, those little twists which earthworms deposit on the ground. Might that be, he wondered, the explanation of the origin of the germs which reappear on the surface? Might not the worms, returning from their subterranean journeys in the immediate neighbourhood of graves, bring back with them splenic spores, and thus scatter the germs so exhumed? That would again be a singular revelation, unexpected but quite simple, due to the germ theory. He wasted no time in dreaming of the possibilities opened by that preconceived idea, but, with his usual impatience to get at the truth, decided to proceed to experiment.

On his return to Paris Pasteur spoke to Bouley of this possible part of germ carriers played by earthworms, and Bouley caused some to be gathered which had appeared on the surface of pits where animals dead of splenic fever had been buried some years before. Villemin and Davaine were invited as well as Bouley to come to the laboratory and see the bodies of these worms opened; anthrax spores were found in the earth cylinders which filled their intestinal tube.

At the time when Pasteur revealed this pathogenic action of the earthworm, Darwin, in his last book, was expounding their share in agriculture. He too, with his deep attention and force of method, able to discover the hidden importance of what seemed of little account to second-rate minds, had seen how earthworms open their tunnels, and how, by turning over the soil, and by bringing so many particles up to the surface by their “castings,” they ventilate and drain the soil, and, by their incessant and continuous work, render great services to agriculture. These excellent labourers are redoubtable grave-diggers; each of those two tasks, the one beneficent and the other full of perils, was brought to light by Pasteur and Darwin, unknowingly to each other.

Pasteur had gathered earth from the pits where splenic cows had been buried in July, 1878, in the Jura. “At three different times within those two years,” he said to the Académie des Sciences and to the Académie de Médecine in July, 1880, “the surface soil of those same pits has presented charbon spores.” This fact had been confirmed by recent experiments on the soil of the Beauce farm; particles of earth from other parts of the field had no power of provoking splenic fever.

Pasteur, going on to practical advice, showed how grazing animals might find in certain places the germs of charbon, freed by the loosening by rain of the little castings of earthworms. Animals are wont to choose the surface of the pits, where the soil, being richer in humus, produces thicker growth, and in so doing risk their lives, for they become infected, somewhat in the same manner as in the experiments when their forage was poisoned with a few drops of splenic culture liquid. Septic germs are brought to the surface of the soil in the same way.

“Animals,” said Pasteur, “should never be buried in fields intended for pasture or the growing of hay. Whenever it is possible, burying-grounds should be chosen in sandy or chalky soils, poor, dry, and unsuitable to the life of earthworms.”

Pasteur, like a general with only two aides de camp, was obliged to direct the efforts of Messrs. Chamberland and Roux simultaneously in different parts of France. Sometimes facts had to be checked which had been over-hastily announced by rash experimentalists. Thus M. Roux went, towards the end of the month of July, to an isolated property near Nancy, called Bois le Duc Farm, to ascertain whether the successive deaths of nineteen head of cattle were really, as affirmed, due to splenic fever. The water of this pasture was alleged to be contaminated; the absolute isolation of the herd seemed to exclude all idea of contagion. After collecting water and earth from various points on the estate M. Roux had returned to the laboratory with his tubes and pipets. He was much inclined to believe that there had been septicæmia and not splenic fever.