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    Untitled Article

    494 Natural Theology . No . VIII . —Mechanical Arrangement 6 f the Body ,

    such is the advantage received from a chain composed of many links , the spine of many bones . The cartilages or gristles , are thicker before than

    they are behind , so that when we stoop forward , the compressible substance , yielding in its thicker paxt , brings the surfaces of the adjoining vertebrce nearer to the being parallel with cue another , instead of increasing the inclination of thsir planes , which would have occasioned a fissure between there . 3 . As the rneflullary canal is to ^ ive out a supply of nerves , notches are made in the

    upper and lower edge of ine vertebrae , which when they are put together , these notches exactly fitting , form small holes , and through these holes the nerves issue cut in pairs to send their branches to every part of the body . Another purpose assigned to the same instrument is the insertion

    ofthe bases of the muscles , and the support of the end of the ribsj for which there is a figure suited to the design . Butt . be strength of the parts , and the security ar / ainst luxation were still to

    be consulted . Lor this purpose , the moveable joints between the vertebrae , so lock in , and overwrap one another , as to secure the body of the vetebrse from being pushed out of its place by any violence short of that which would break the bone . An instance of this may be seen in the chine of a hare . Hence the spine is to be considered under three views , \ iz . its articulations , its ligdmen ^ s , and its perforations , from winch the body derives advantages with regard to action , strength , and a secure communication with the brain .

    The structure of the spine is different in different animals . In the serpent tribe it is considerably varied ; but with a strict reference to the conveniency of the animal . For , whereas in quadrupeds the number of vertebrae is from thirty to forty , in the serpent it is nearly a hundred and fifty : in men and quadrupeds the surfaces of the bones are flat , and these are bound

    tight by sinews : in the serpent the bones play within one another like a ball and socket ; so that they have a free motion upon one another in every direction : thus in men and quadrupeds firmness is more consulted 9 in serpents pliancy ; but pliancy is not obtained at the expense of safety . " The back-bone of a serpent for co-

    Untitled Article

    herence and flexibility is one of the most curious pieces of animal mechanism with which we are acquainted The chain of a watch which passes between the spring-barrel and fUSee and -which aims at the same properties ' " is but a bungling piece of workman- ' ship in comparison with that of which 11

    we are speaking . See Palev ' s Nat Theol . The first vertebra of the neck is named the atlas , from the circumstance

    of the globe of the head being placed upon it . Its processes are scarcely distinguishable } it has no body and is in fact simply a ring through which the spinal m&rcow passes from the

    great hoie cf the scull into the rest of the tube formed for its reception . No mechanism was ever contrived more evidently artificial than that seen in the vertebrae of the human neck .

    Two tilings were wanted : the headwas to have the power of bending forward and backward ; and at the same time of turning itself round upon the bodv to a certain point . For this ..

    two contrivances are employed . 1 . The head rests upon , the uppermost of the vertebrae , and is united to it by a hinge-joint , upon which it plays freely backward arid forward * < 2 . For the

    rotatory motion , there is mechanism resembling a tenon and mortice , not between the head and the uppermost bone in the neck , but between that bone and the bone next underneath

    it . This secondjbone has a projection like a tooth , which entering- a socket in the bone above it , forms a pivot , upon which that upper bone , together with the head which it supports , turns freely in a circle , as far as the muscles will permit . Thus , when we nod , we make use of the hinge-joint , when we turn the head we use the tenon and

    mortice . The same contrivance is employed in mounting a telescope . For the vertical motion , thereisahinge upon which the telescope plays : for the horizontal motion an axis upon which the telescope and the hinge turn round : " and this , " says Dr . Paley ,

    " is exactly the mechanism which is applied to the motion of the head ; nor will any one here doubt of the existence of counsel and design , except it be by that debility of mind which can trust to its own reasonings in nothing-The pelvis extended to give a steady bearing fo the trunk and to connect it with the lower extremities , is » - cir-

• Citation
  • Monthly Repository (1806-1838) and Unitarian Chronicle (1832-1833), Aug. 2, 1815, page 494, in the Nineteenth-Century Serials Edition (2008; 2018) ncse.ac.uk/periodicals/mruc/issues/vm2-ncseproduct1763/page/30/