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

  • George Murray Humphry
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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    the vertebral centres, and enclosing the neural and haemal canals, extend to the upper and lower margins of the animal, and constitute the boundary lines between the parts formed in the ascending neural and the descending haemal layers of the two sides. With lateral perforations for nerves and vessels and with lateral intermuscular processes they form, together with the notochord, the primitive skeleton, as instanced in the Lancelet. They give off laterally processes or sheets which form the intermuscular septa of the great lateral muscle; and at the parts where there are no hns (fig. 2) they give off, near the upper and lower edges of the body, oblique processes which enclose the supra- and infra-carinales muscles, while the septa themselves are continued, in the middle line, between the cari- nales of the two sides to the skin. The dorsal and anal fins occupy the place of the carinales. Accordingly a membranous process from each septum passes on either side of the fin and its muscles, separating it from the edges of the lateral muscle, while the septum itself is continued to, and blends with, the interspinales bones. This may be seen in the transverse sections, and is better seen by stripping off the muscles on the sides from the interspinous bones and the spines of the vertebrae, when both sets of bones will be found to be enclosed in, and connected with one another and with those in front and behind by, one continuous membranous sheet. The blood-vessels and nerves may at the same time be displayed passing on either side of this sheet, in each interv^al between the spinous pro¬ cesses, to the fin. In a Pike about a foot long, from which the accompanying drawings were made, I found the large or distal ends of the interspinous bones, both neural and haemal, composed of car¬ tilage. In the deeper parts of the mesial septum, above and below, at the lines of junction with, or giving off of, the transverse intermuscular septa, the neural and haemal spines are formed; and deeper still, where the coalescence of the two sides of the septa is prevented by the presence of the neural and haemal tubes, the neural arches are formed. In the abdominal part of the animal (fig. 3) the presence of the viscera causes the visceral or descending embryonic laminae to take a wider sweep, 1—2
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