On the homological relations to one another of the mesial and lateral fins of osseous fishes / by Professor Humphry.

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

Licence: Public Domain Mark

Credit: On the homological relations to one another of the mesial and lateral fins of osseous fishes / by Professor Humphry. Source: Wellcome Collection.

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    From the Journal of Anatomy and Physiology, Vol. V. ON THE HOMOLOGICAL RELATIONS TO ONE AN¬ OTHER OF THE MESIAL AND LATERAL FINS OF OSSEOUS FISHES. By Peofessor Humphry. PI. II. The use of the terms ‘ median ’ and ' lateral ’ with reference to the fins of fishes, though founded on obvious facts, appears to me nevertheless to have in some measure the effect of con¬ tributing to maintain a misconception with regard to the real nature of those parts and their relation to oiie another and to surrounding structures. More especially is this so foras¬ much as the term ‘ median ’ is by anatomists pointedly con¬ trasted with ‘ lateral ’ when they are indicating as one among the special features of fishes that certain of their locomotory organs are placed in the middle line. The most rudimentary knowledge of development tells us that, with the exception of the parts lying in the axis of the body, none are really mesial, that is, formed in the middle line. All are formed in the lateral layers which ascend or descend from the axial line. The most, therefore, that we can say of any part is that it has acquired a mesial position and character by the coalescense of two lateral elements in the middle line. This must be the case with the dorsal, caudal and aual fins of fishes; and it is in this way that, though not essentially median organs, they have acquired their claim to that title. Nor is this an unimportant distinction, especially when we seek to compare them morphologically with other structures. Each of these fins, like the tongue and every other organ mesially situated, and at a distance from the axis, is a double organ and may be the representative of any other organ which is actually double, in which, that is, the two lateral constituents have not coalesced b 1 A similar view was, I find, entertained by that eminently philosophical anatomist, John Goodsir. After giving his reasons for considering that the interspinous hones and mesial fin-rays are elements of the neuro- or endo- skeleton, he goes on to say; “With reference to the mesial position and charac¬ ters of these bones, I would remark, that it appears to me quite permissible, on morphological grounds, to look upon eacli interspinous bone, with the correspond¬ ing fin-ray, as consisting of a right and left actinapophysis mesially united— that is, to consider the right and left halves of which they consist in the young 1