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

  • Sibson, F. (Francis), 1814-1876.
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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    gives off a slip that ascends in front of the neck of the sac, and passes over it to he inserted into the anterior wall of the outlet. When the posterior or frontal bellies of these muscles act on both sides, they will form a sling which will draw backwards the anterior wall of the breathing canal, and compress it against the posterior wall, thus closing the canal below the openings of the anterior sacs. They will, I conceive, at the same time contract the outlets of the sacs. The anterior heads, or those from the maxillary bone, will draw forward the sling formed by the combined muscles and open the breathing canal. These two muscles cross each other, so that in the same muscle the anterior belly is most superficial, while the posterior belly is deepest. The most superficial of these tendinous slings is blended with the tendinous struc- ture common to a very strong pair of muscles (24*). These muscles arise from the superior maxillary bones to the side of the anterior deep pouch, and ascend over the sides of that pouch to be inserted into the strong gristly tendon (fig. 1-24) at the top of it. The combined muscle forms a long arched musculo-tendinous bridge over the anterior deep sac, that, when it contracts, compresses the sac. The tendinous bridge just described passes backwards underneath the two tendons (fig. 1-22.23) that close the deep portion of the breathing canal; it then turns upwards behind those tendons, and is reflected forwards over them to form the insertion of two other muscles (fig. 2-10) that are superficial to the muscles just described. The combined musculo-tendinous web formed by these two muscles and their common tendon, superficial to the muscles described above, arches over the anterior deep sac; with those muscles it combines to contract the anterior deep sac., A distinct set of fibres (40*) arises from the side of the inlet of the osseous canal; these fibres pass forwards and upwards over the neck of the anterior deep pouch, to be inserted into the central tendinous web covering that pouch, the outlet of which, this muscle, I conceive, contracts. Another muscle, (41*) just behind this, seems to have a similar function. The anterior deep pouch (2.) differs from the other pouches in having no superficial wrinkles, and in having a regular muscular coat; it seems indeed to be rather a pouch- like dilatation of the breathing canal, than one of the regular sacs. Each posterior deep pouch (fig. 1. 2-3) is situated behind the breathing canal, be- tween it and the frontal bone. Its opening is horizontal, and looks downwards, and is half-surrounded in front by a cartilage (fig. 1-21). Several fan-like, half-pouch formed muscles (16.17-18.19*), that arise from the frontal bone, contract and empty the posterior pouch. To contract the mouth of the pouch there are two muscles. One (fig. 1-20) springs from the side of the central protuberance of the frontal bone, and forms a tendon that passes forwards and inwards encircling the inner side and front of the outlet :