"It will be understood that these two propositions are merely hypothetical. If sustained by analogies, subsequent observations, and experience, they will be accepted as truths; if not thus sustained, they will of course be rejected. "The extensive prevalence of the cholera, over large portions of the globe, commencing in the year 1818, led medical men to seek for its cause. Dr. Cowdell, of London, in 1848, published 'A Disquisition on Pestilential Cholera, being an attempt to explain its phenomena, nature, cause, prevention and treatment, by reference to an extrinsic fungous origin.' "In 1849, Prof. J.K. Mitchell, of Philadelphia, issued a more elaborate work, 'On the Cryptogamous Origin of Malarious and Epidemic Fevers.' It abounds in numerous facts and correct reasoning, and should be consulted by every investigator of disease, animal and vegetable. "These publications attracted the attention of the medical profession, both in America and Europe, so long as that epidemic continued its ravages, and the theories they advanced gained extensive credence during that time. They were, however, lost sight of when that epidemic subsided. Recently they have been substantiated as plain matters of fact, so far as malarious diseases are concerned, by the labors and investigations of Prof. J.H. Salisbury, of Cleveland. "It is well established, then, that a number of diseases of the animal system are produced by fungi. 'Under this name botanists comprehend not only the various races of mushrooms, toadstools, and similar productions, but a large number of microscopic plants, forming the appearances called mouldiness, mildew, smut, rust, brand, dry rot, etc.' They are universally diffused in nature. It is difficult to conceive of a place where they do not exist. They are among the most numerous of all plants, in regard to genera and species, and with very few exceptions are deleterious in their impressions on the animal system. Even the palatable mushroom is always poisonous to some persons, and may become so to all under certain circumstances. It is equally evident that fungi frequently occasion diseases in the vegetable kingdom. The smut of wheat and maize, the rust of wheat, ergot of rye and grass-seeds, and specks, cracks, and discoloration of the skin of the apple and pear are of this nature. "The microscopical examinations of Prof. Salisbury and others have detected the presence of certain species, infesting extensively pear trees about the period of attack by the blight. They have made similar discoveries that lead to the conclusion that the curl of the peach leaf, the potato disease, and the blight of pear trees, all have their origin from the cause assigned in my second proposition.