Louis Pasteur: His Life and Labours

ence of a problem requiring solution, caused him at once to forget the sacrifices he had made in quitting his laboratory at the école N

d been reproduced in the country, had arrived at their fourth moulting and had a very bad appearance. But, strange to say, on examining with the microscope a number of chrysalides and moths of the group which had so delighted its proprietor, Pasteur found corpuscles almost always present, whereas the examination of the worms of the bad group only exhibited them occasionally. This double result struck Pasteur as very strange. He at once sent messengers into all the neighbourhood of Alais to seek for the remains of backward cultivations. He attached extreme

er his arrival, that it was a mistake to seek for the corpuscle in the eggs or in the worms. Both the one and the other could carry in them the germ of the disease, without exhibiting distinct corpuscles, visible under the microscope. The evil developed i

ry corpusculous couples, intending to wait for what these eggs would produce the following year; the first would be probably free from corpuscles, while the latter would contain them. He would thus have in future, though on a small scale, samples of originally healthy and of originally unhealthy cultivations, by the compari

was objected that the labours of several Italian savants had established beyond all doubt that the corpuscles were a normal element of certain worms, and especially of all the moths when old; that other authors had affirmed it to be su

ia; 'your selected eggs will produce healthy worms, but these worms will beco

l experiment had pronounced upon it with precision. All scientific research, in order to be undertaken and followed up with success, should have, as point of departure, a preconceived idea, an hypothesis which we must seek to verify by

ed in by mountains, up the sides of which terraces rise, one above the other, planted with mulberry trees. The solitude was profound. Madame Pasteur and her daughter constituted themselves silkworm-rearers-performing their part in earnest, not only gathering the leaves of the mulberry trees, but also taking part in all the experiments. The assistants of

certain; the majority, however, either doubted or denied its existence; some considered it as accidental. It was said, for example, that the evil was not contagious by itself, but that it became so through the presence and complication of other diseases which were themselves contagious. This hy

existence of a poisonous medium rendered epidemic by some occult influence. Pasteur soo

not present. Matters remained in this state for some days longer. Even the third moulting was got through without any marked difference between the two groups of worms. But soon important changes set in. The corpuscles, which had hitherto only showed themselves in the integuments of the intestines, began to appear in the other organs. From the second day following the third moulting-that is to say, the twelfth after the infection-a visible inequality distinguished the infected from the non-infected worms. Those of the standard lot were clearly in much the best health. On examining the infected worms through a magnifying glass, a multitude of little spots were discovered on their heads, and on the rings of their bodies, which had not before shown

tion, since it was only on the twelfth day that it became perceptible. Finally, the spots of pébrine on the skin, far from being the disease itself, were but the effect of the corpuscles developed in the interior; they were but a sign, already removed from the tr

s, were faithfully reproduced. Pasteur created at will any required manifestation of pébrine. When he infected quite healthy worms, after their fourth moulting, with fresh corpusculous matter, these worms, even after several meals of corpusculous leaves alternated with meals of wholesome leaves, made their cocoons. It might have been supposed that in this case the contagion had not taken effect. This was but a deceptive appea

n selected. He fed these healthy worms on leaves over which a clear infusion made from the remains of moths or worms exempt from corpuscles had been spread with a paint-brush, instead of lea

ich had succeeded perfectly well as far as the production of cocoons was concerned. It was proved that almost invariably the following year the eggs of these fine-looking groups were unproductive. Numbers of the agricultural boards, and practitioners, not being able to believe in the existence of the disease in collections that were so satisfactory as regards the abundance and beauty of the cocoons, persisted in thinking that the failures had an origin not connected with the seed itself. This resulted in deception after deception, often even in mistakes that were

food charged with corpusculous débris, it might be asked how, in the industrial establ

f the intestinal canal. It is there that they swarm. It is easy to understand that these excreta, falling on the leaves, contaminate them all the more easily because the worms, by the weight of their bodies in crawling, press the excreta against the leaves. This i

re capable of carrying the seeds of disease to other healthy worms, which may be pricked in their turn. To demonstrate experimentally, as Pasteur did, the existence of this cause of contagion, it was only necessary to take some worms and allow them to wound each other. Lastly, infection at a distance, through the medium of the air and the dust it carries, is a fact equally well established. It is sufficient, by sweep

l cultivations conducted in nurseries which had totally failed from the effects of pébrine the year before. The explanation is, as shown by Pasteur, that the dust can only act as a contagion when it is fresh. Corpusculous matter, when thoroughly dried, loses its virulence

moth will emerge, as a chick emerges from its egg. Let anyone imagine this origin of an approaching life, no longer in its normal purity, but associated with a parasite which will find in the materials surrounding it, so adapted to life and transformation, the elements of its own nourishment and multiplication. This parasite will be present when

hereditary, helping us to understand the evolution of this