On the blow-hole of the porpoise / by Francis Sibson ; communicated by Thomas Bell.

  • Francis Sibson
Date:
1848
Catalogue details

Licence: Public Domain Mark

Credit: On the blow-hole of the porpoise / by Francis Sibson ; communicated by Thomas Bell. 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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    opening uppermost, and retain that opening above the surface of the water during sleep and during the act of copulation. The muscles that open and close the blow-hole, and that act upon the various sacs, form one of the most complicated yet most exquisitely adjusted pieces of machinery that either nature or art presents. The blow-hole is stretched open, in front, by two muscles (fig. 2-6) that act from the superior maxillary bones, to draw forward the cartilaginous mass in front of the outer opening; behind, by muscular fibres (fig. 2-7) that act from the frontal bones on the posterior and lateral edges of the blow-hole. To close the blow-hole, two sets of muscular fibres (fig. 2-5) spring from the frontal bone, pass obliquely forwards and inwards, one to each side of the opening, and are inserted into the gristly mass (fig. 2-4) in front of the blow-hole. When they act, they draw this gristly mass forcibly backwards, and close the blow-hole by pressing its anterior and posterior walls together, and compressing them against the posterior pouches and the prominence at the centre of the frontal bone. A set of muscular fibres (fig. 2-8) arises from the circuit of a depression formed on the cranium to each side of the bony canals; these fibres pass over the anterior lateral pouch, blending with the muscles that close and open the blow-hole. On removing this, a covering of muscular fibres (fig. 2-8 a) that cling round the sac is exposed; these arise from the anterior lateral part of the superior maxillary bones, and pass upwards and backwards to form a muscular envelope for the pouch on its inner and posterior surface ; the fibres return forwards to be inserted into the outer and anterior walls of the blow-hole. A fan-like muscle (fig. 2-9) arises from the circuit of the depression to be inserted into the posterior and lateral walls of the blow-hole; this assists in opening it by spreading apart its walls. On removing this fan-like muscle, a remarkable series of similar fan-like muscles (11.12.13.14.15*) is exposed. These lie one above the other, and arise by muscular fibres from the circuit of the depression ; the fibres of each converge to a tendinous aponeurosis thinner than paper. Four or five of these fan-like thin muscles may be removed by careful dissection, one after another ; they act to expand different parts of the outlet of the anterior lateral sac, to draw backwards and expand the posterior walls of the great respira- tory canal, and to compress the posterior deep sacs. On removing these, two remarkable muscles (fig. 1. Archives, fig. 7-22.23) are brought into view that have each a double muscular origin, one from behind forwards from the frontal bone (22 a. 23 a*), meeting another from before backwards and inwards from the superior maxillary bone (22 b. 23 b*). These two origins combine in each to form a tendon ; these tendons (22.23) pass forwards in front, and below the neck of the anterior pouch, where they unite with their fellows ; each of these tendons * These numbers refer to drawings that are in the Archives of the Royal Society.
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