Mechanical theory of the predominance of the right hand over the left, or, more generally, of the limbs of the right side over those of the left side of the body / by Andrew Buchanan.

  • Buchanan, Andrew, 1798-1882.
Date:
1862
Catalogue details

Licence: Public Domain Mark

Credit: Mechanical theory of the predominance of the right hand over the left, or, more generally, of the limbs of the right side over those of the left side of the body / by Andrew Buchanan. Source: Wellcome Collection.

Provider: This material has been provided by The University of Glasgow Library. The original may be consulted at The University of Glasgow Library.

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    as mere appendages of his body, and separately from it, he uses those of either side with a like efficiency; but when he becomes capable of making all the muscles of his frame—of trunk and limbs—co-operate in producing a combined effort, which nature prompts him to do as soon as he has strength to accomplish it, then for the first time he becomes conscious of the superior power of his right side—a power not prim- arily due to any superior force or development of the muscles of that side, but to a purely mechanical cause. He cannot put forth the full strength of his body without first making a deep inspiration; and by making a deep inspiration, and maintaining afterwards the chest in an expanded state, which is essential to the continuance of his muscular effort, he so alters the mechanical relations of the two sides of his body that the muscles of his right side act with a superior efficacy; and to render the inequality still greater, the muscles of the left side act with a mechanical disadvantage. The consequence is, that the muscles of the right side are called into action in preference on all great occasions where muscular power has to be put forth; and, from being more fre- quently exercised, they become more highly developed, stronger, and more prompt to action. The full predominance of the right side is thus ultimately established. One limb of the syphon has been made longer than the other, and the whole current sets in that direction. With the view of establishing this doctrine I shall first endeavour to prove certain preliminary propositions with respect to the position of the centre of gravity of the body, the changes in the position of it produced by the act of respiration, and the connection between the act of respiration and muscular exertion; and I shall thereafter point out the mechanical principles which render the inclination of the centre of gravity of the body to the right side the primary cause, and at all times one of the principal causes, of the superiority of the limbs of the right side over those of the left. The whole argument thus divides itself into two parts, the proof of the first of which is chiefly experi- mental, or derived from general reasoning, while the proof of the second is chiefly demonstrative. But I shall add a third part, contain- ing some evidence not strictly belonging to either of the former heads, or omitted in its proper place, not to encumber the general argument. A- Preliminary Propositions. 1st. The centre of gravity of the body situated not in the mesial plane, but to the right side of it.—Borelli found the centre of gravity of the body to be situated between the hips and the pubis, or in the middle of the pelvis. His experiment was made by poising a table accurately on the edge of a triangular prism placed under it trans- versely, and laying thereupon a dead body, which he shifted upward