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Show 1884.] DISEASES OF CARNIVOROUS MAMMALS. 181 late in appearance. Death is usually brought about after this manner. The animal suffers from paralysis of the hind quarters, which gradually ends in paraplegia to such an extent that it is absolutely necessary to kill it. The paraplegia is brought about, as I have explained above, by pressure on the cord due to proliferation of the epiphysial structures, and this is the most important feature of the disease. For the vertebral plates at this age are, of all parts of the skeleton, the seat of the most active growth, just as in infancy the epiphyses of the long bones are undergoing extensive and rapid metamorphosis. The cord, when examined microscopically at the seat of compression, shows an increased quantity of neuroglia, a diminished number of axis-cylinders, fatty granules in abundance, and destruction of tbe nerve-cells in the grey matter. 2. Mollities Ossium.-This singular affection is met with in thoroughly adult carnivorous animals ; it is a rare affection. My best and most characteristic case was from the Racoon-like Dog (Nyc-tereutes procynides). The chief features of the disease are these :-Beading of the ribs is wanting ; softness of the bones is replaced by hardness and brittle-ness, so that they break easily ; deformity of the long bones may be present to an extreme degree; the alveolar margins of the jaws absorb, allowing the teeth to fall out. When the bones are macerated and dried, they become as light as cork. Paraplegia is a constant feature of the disease. Summarizing these three forms of bone-disease arising from constitutional causes, however varied their manifestations, the aetiology is the same, viz. loss of exercise and active life, artificial mode of feeding compared with their wild state of living, and the vicissitudes of an English climate. Indeed, if referring to the human subject, it would be expressed in one terse sentence, " Bad hygienic conditions incident to the life of a captive." There can be no doubt that the different effects of the disease on the system are due simply to the fact that, at these different epochs of life, physiological processes taking place in a growing bone differ very materially, and as disease is to be regarded as a perversion or exaggeration of normal physiological processes, so we have an example of an alteration of the normal processes which should be in operation during infancy producing "rickets," at puberty "late rickets," and in adult life, when there are no epiphyses for the disease to attack, but " osteoporosis" is in full vigour, perversion leads to " mollities ossium." There seem to be two rules regarding pathological manifestations. (a) Acute diseases attack those parts where the blood supply is greatest, and as a consequence growth is rapid. (b) Functionless organs are prone to undergo degeneration or to become the seat of cancer, &c. Respecting the first rule:-In infancy the long bones are the seat of very active changes, particularly at the epiphyses ; hence they become affected with rickets. At puberty, the vertebrae are developing their secondary centres, so they |