A comparison of the shoulder bones and muscles with the pelvic bones and muscles / by Professor Humphry.

  • Humphry, George Murray, Sir, 1820-1896.
Date:
[1870?]
Catalogue details

Licence: Public Domain Mark

Credit: A comparison of the shoulder bones and muscles with the pelvic bones and muscles / by Professor Humphry. Source: Wellcome Collection.

    14/24 (page 80)
    the lateral tubercles are blended into one ventrally-placed spine. Fourthly, the rotation of the fore and hind limbs in opposite directions necessarily tends to increase the confusion. It does so, not simply by reversing the relative position of the muscles, but, I think, also by impressing in some instances an opposite developmental tendency upon the muscles of the two limbs and causing them to be directed in each towards that margin or that tubercle which will be most appropriate to their action in the final position of the limb. This seems to me to be an explanation of the fact which has been the source of so much embarrassment to homologists, and which indeed precludes an exact serially homological comparison of the fore and hind limbs, viz., that the muscles from the dorsal aspect of the scapula pass to the radial tubercle of the humerus, while those from the dorsal aspect of the ilium pass to the fibular tubercle of the femur. Those tubercles in the two limbs, though homologically different, yet in size, in position, in function, and to some extent also in muscular relations, are made to answer to one another. That the course of muscular transformation in the embryonic plasma should be thus conformed to the future requirements of the two limbs is no more than other modifications would lead us to expect; especially when we find the dispositions just referred to, of the latissimus dorsi in birds and saurians, and of the tibialis anticus in Manis, presenting instances of a like kind in corresponding limbs. Fifthly, more numerous are the infringements of serial homological order presented by the blood-vessels and nerves passing to the several muscles in the two limbs. The blood¬ vessels are perhaps the most conformable of animal structures, which is no more than would be expected from their mode of formation and their disposition, and they give us very little help in our present task. From the nerves, more of definiteness in arrangement and tenacity of serial homology is to be ex¬ pected, than from the blood-vessels. Still, when we mark the differences in the disposition of the nerves in the two limbs, and the intricate manner in which the nerves passing to the limbs are respectively blended in the cervical and the lumbo-sciatic plexuses, our confidence in any readily available assistance from