The palpebral and oculomotor apparatus in fishes : observations on morphology and development / by N. Bishop Harman.

  • Harman, Nathaniel Bishop, 1869-1945.
Date:
[1899]
Catalogue details

Licence: Public Domain Mark

Credit: The palpebral and oculomotor apparatus in fishes : observations on morphology and development / by N. Bishop Harman. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    to a dorsal musculature arranged in a characteristically laminated and symmetrical fashion. The branchial muscles have increased in size, the deeper part to the greater extent; the connection of tlie deep part with the branchial cartilages is distinct, whilst the superficial -can in parts be traced into a veiitro-lateral ex- tension. The connection of the conjoined dorsal extremity of both superficial and deep portions with the superficial dermis is more pronounced. The dorsal musculature has now extended over the auditory invagination for some distance ; but, occupying a position still anterior to this, the branchial muscle can be traced; it forms two parts, a small superficial mass of cells lying beneath the surface epiblast in close connection with the roof of the spiracle, beyond which it cannot be traced, and a deeper portion which is more differentiated as muscle tissue, and can be traced, anteriorly to the spiracle, into connection with the maxillary cartilage. In the hinder sections both these portions unite in the dorsal region. In the fourth embryo, ‘ E,’ the state of the general muscular development shows a considerable advance on the former. As regards the spiracle region, the same masses of muscle described in the previous paragraph are to be seen. From a common mass situated dorso-lateral to the spur of the auditory capsule (fig. 11) they separate out as a maxillary mass and a spiracular mass (fig. 12); the former passes to the maxillary cartilage and the latter to the skin in the region of the spiracle. Besides these masses there is a new and third mass which appears first in the region of the branchial bar, which is the second after the spiracle, as a thin streak of cells lying in the superficial meso- blast of the dorso-lateral region (fig. 11); tracing this forwards, it is found to become shorter and thicker and more definite, until nearing the spiracle it forms a sharply defined mass of cells of small size, closely applied to the angle formed between the roof of the spiracle and the skin. A few sections further forwards the other spiracular mass separates from the ma-Villary mass and blends with this third mass, and the two make a single mass of coitsiderable size upon the roof of the spiracle (fig, 12). A part of this mass remains closely applied to the skin after the spiracle has been passed (fig. 13), when it becomes elongated and extends somewhat ventrally ; later it separates into two portions, a B