The principles of anatomy and physiology applied to the preservation of health / by Joseph Brown Walker.

  • Walker, Joseph Brown.
Date:
1844
Catalogue details

Licence: Public Domain Mark

Credit: The principles of anatomy and physiology applied to the preservation of health / by Joseph Brown Walker. Source: Wellcome Collection.

Provider: This material has been provided by the National Library of Medicine (U.S.), through the Medical Heritage Library. The original may be consulted at the National Library of Medicine (U.S.)

    9/32
    [9] reader several considerations of a more general and di- rectly useful nature. And here I shall quote largely from Dr. Combe : Bones consist of two kinds of substances, those of an animal and those of an earthly nature. To the former belongs every thing connected with the life and growth of bones, and to the latter the hardness and power of resistance by which they are characterized.— The relative proportions of the animal and earthy consti- tuents vary, however, according the period of life. In infancy the animal portion greatly predominates, and, consequently, the bones are at that age comparatively soft, yielding and elastic. In middle life the proportions are more equally balanced, and while the bones thereby acquire great hardness and solidity, they still preserve some elasticity. In old age, on the contrary, when the earthy constituent predominate, they become dry, brittle, and comparatively lifeless. A very important purpose is served by the different proportions which the animal elements of bone bear to the earthy, at different ages. In early youth, when much strength is not wanted, as the body is not exposed to se- vere efforts, but when a greater growth of bone is requir- ed to complete the development of the human frame, the animal or living part of the bone is observed to be pre- dominant. But. in middle life, when growth is finished, and when nutrition is required only to repair waste, a larger proportion of the solid or earthy, and a smaller proportion of the vital constituents becomes necessary. In old age, again, when the wants of the system are reversed, and when positive diminution of existing mass- es is required to put the frame into harmony with the shrunk muscles and feebler powers of life, the absorbent vessels carry away more of the vital matter, leaving chiefly the earthy, which, being less susceptible of change, requires scarcely any support from within ; and hence the brittle and compact hardness of bones, and their little capability of uniting when fractures happen at an ad- vanced period of life. At birth, many of the bones are, properly speaking, of a cartilaginous nature. As the bones increase in growth, the cartilage is removed by the