Reports on the diseases of cattle in the United States made to the Commissioner of Agriculture, with accompanying documents. / Department of Agriculture.

United States Department of Agriculture

Date:: 1869

Credit: Reports on the diseases of cattle in the United States made to the Commissioner of Agriculture, with accompanying documents. / Department of Agriculture. Source: Wellcome Collection.

Provider: This material has been provided by Royal College of Physicians, London. The original may be consulted at Royal College of Physicians, London.

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$point. The voice, of the ablest and most oarefnl observers, who liave studied pleuro-pneumonia practically, is unanimous on the point; and although in every country the tendency has been at flrst to re{,'ard this insidious disease as orij>inating- from atmospheric agencies, when the facts have been probed by skillful men, the earlier o])inions have been rejected. Gerlach, in 1835, Delafond, in 1844, and Sauberg, in 1840, publishe 1 very abundant and conclusive testimony on this point. THE PATHOLOGY, OE NATUEE OF THE LITSG PL AGUE. There is nothing more dangerous and better calcidated to retard inquiry and truth than the common practice of speculating as to the nature of specific diseases in men and animals by the analogical method. Bovine pleiuo-pneumonia has been widely supposed to be an inflammation o^ the lungs, governed by the same conditions that operate in relation to ordinary inflammations of the chest in the human family, antl, indeed, in all mammalia. The characteristic signs of small-pox depend on a cuta- neous inflammation, but have apperances different from the results of a scald. It is as rational to define variola inflammation of the skin as it is to declare that the lung disease of cattle is an inflammation of the air ijassage and lungs. The local iihenomena of the disease are associated with and characterized by inflammatory changes, but the cause in operation inducing all this is peculiar and specific. The lung plague is a malignant fever, never generated de novo, so far as reliable observation has yet reached, dependent on the introduction of a virus or contagion into the system of a healthy animal. This prin- ciple produces a local change if inserted into any part provided with a connective or fatty tissue, in which it most readily penetrates. The same local change is produced by its contact with the delicate mucous surface of the bronchial tubes. It adheres, spreads not unlike cancer, regard- less of the nature and importance of the structure it invades, and traverses the lymphatic vessels to form deposits in the neighboring lymphatic glands, but not generally throughout the lymphatic sys- tem. At first there is no great intensity of inflammation. Suppuration is only a later complication from the concomitant non-specific change in masses of areolar or connective tissue. Congestion and a serous infiltration rapidly surround the spot inoculated. Heat, redness, pain, and swelling manifest themselves, and the reproduction and extension of the tissue-destroying virus may be judged by the extent of swelling; the amount of the yellow gelatinous serosity or exudation which fills the lung tissue, thickens white fibrous structures, blocks up the adipose tissue corpuscles out of which the fat is displaced, and is only limited iu many casts by the amount of connective tissue it can invade, by gra%'i- tation or otherwise, and the endurance of the animal under a process so prostrating and depletive. That all this happens, we have tested by experiment. A susceptible animal is inoculated in the dewlap, and at the expiration of a week or$