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 pro- 

 liferation of the epiphysial structures, and this is the most im- 

 portant 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 the 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 (Nye- 

 tereutes jprocynides). 



The chief I'eatures 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 mace- 

 rated and dried, they become as light as coik. 



Paraplegia is a constant feature of the disease. 



Summarizing these tliree forms of bone-disease arising from con- 

 stitutional 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 ex- 

 ample 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. 



(ff) Acute diseases attack those parts where the blood supply 

 is greatest, and as a consequence growth is rapid. 



(b) Functioidess 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, particu- 

 larly at the epiphyses ; hence they become affected with rickets. At 

 puberty, the vertebrae are developing their secondary centres, so they 



