observations of Darwin as set forth in his last work on "The Formation of Vegetable Mould Through the Action of Worms." Darwin has shown beyond all dispute, as the result of his incomparable researches, that though "the plough is one of the most ancient and most valuable of man's inventions, long before he existed the land was in fact regularly ploughed, and still continues to be ploughed, by earthworms." He has shown us that the smoothness which we admire in a wide, turf-covered expanse "is mainly due to all the inequalities having been slowly leveled by worms," and that "the whole of the superficial mould over any such expanse has passed, and will pass again, every few years, through the bodies of worms!" It was left for Pasteur to show that these innumerable and indefatigable plowmen, whilst rendering to man such efficient service, may also be the carriers of the seeds of disease and death. In proceeding with our brief historical account of Pasteur's and allied researches, we are arrived at the point where their analogy to Jenner's becomes manifest, and where their direct bearing on the welfare of mankind comes into view. So soon as it was known that these disease germs were low forms of vegetation, and that, like other vegetables, they could be cultivated, it was natural to ask whether, like other vegetables, their characters and properties could not be so modified as to render them at least less deleterious. Every one knows the difference between the crab-apple and its cultivated variety, the sloe and the plum, the wild and the cultivated celery. It is all the difference between unwholesome and wholesome food. Two methods of cultivation, with a view to obtaining the desired modification of the power exercised by the bacilli and other similar germs, presented themselves, the one analogous to that really pursued by Jenner where small-pox, or the grease of the horse, was passed through the system of the cow, and then from one human being to another; and the second by carrying on the cultivation out of the living body. Both these plans have been adopted, with the result of proving that the potency of the germs can be so diminished as to render the disease produced by their introduction so mild as to be of no importance. Pasteur cultivated the bacillus in chicken broth or meat juice, and allowed a certain time to elapse before he made use of the mixture. After allowing only two months to elapse, the virulence of the germs seemed to be but little impaired, but after three or four months animals inoculated with the fluid, though they took the disease, had it in so mild a form that the greater number recovered. After a long period of six or eight months the engendered disease was so mild that all the animals speedily recovered and regained health and strength.