File:Animal and vegetable physiology, considered with reference to natural theology (1836) (14784620013).jpg

Identifier: animalvegetable01roge (find matches)
Title: Animal and vegetable physiology, considered with reference to natural theology
Year: 1836 (1830s)
Authors: Roget, Peter Mark, 1779-1869
Subjects: Biology Physiology Plant physiology Natural theology
Publisher: Philadelphia, Carey, Lea & Blanchard
Contributing Library: NCSU Libraries
Digitizing Sponsor: NCSU Libraries

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ole diameter. Now if we consider that the principalmechanical property required in everycylindrical lever is rigidity, and moreespecially the power of resisting forcesapplied transversely, that is, tending tobreak the cylinder across, we shall soonperceive, that a given quantity of materialscould not possibly have been disposed in a manner better cal-culated for such resistance than v/hen in the form of a tube,or hollow cylinder.* To this mechanical principle I havealready had occasion to advert, when speaking of the hollowstems of vegetables, which derive their chief strength fromtheir possessing this form;! and we now find it again ap-plied in the structure of bones, which by having been madehollow, are rendered considerably stronger than if the samematerials had been collected into a solid cylinder of thesame length. We may farther remark, that as it is in themiddle of the shaft that the strain is greatest, so it is herethat the cavity is largest, and the resistance most effectual.
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* An elaborate mathematical demonstration of this proposition was longago given by Dr. Porterfiekl, in a paper contained in the first volume ofMedical Essays and Observations, publislied by a Society in Edinburgh,p. 95. t P. 70. OSSIFICATION. 263 § 3. Formation and Development of Bone. But it is not enough to contemplate the purposes so admi-rably answered by tliesc arrangements. Our curiosity can-iiot but be powerfully excited to learn what processes and re-fined series of means are employed by nature to raise and toperfect all these artificially contrived structures. It fortu-nately happens that in this instance we are permitted topenetrate a little farther than usual into the secrets of orsjanicevolution: for the succession of changes can be better followedby the eye in the slow development of the harder parts, thanin the quicker growth of mere yielding and expansible tex-tures. The peculiar material, also, of which bone is formed,is easily distinguished by its hardness, its white

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