Observations in myology : including the myology of Cryptobranch, Lepidosiren, dog-fish, Ceratodus and Pseudopus pallasii, with the nerves of Cryptobranch and Lepidosiren and the disposition of muscles in vertebrate animals / by G.M. Humphry.

Date:: 1872

Credit: Observations in myology : including the myology of Cryptobranch, Lepidosiren, dog-fish, Ceratodus and Pseudopus pallasii, with the nerves of Cryptobranch and Lepidosiren and the disposition of muscles in vertebrate animals / by G.M. Humphry. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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$5. Coraco-hrachiali's quartus {suhscapularis) arises from the margin of the coracoid and also of the scapula forming the inner edge of the glenoid cup, extending from the origin of the coraco-brachialis hrevis to and over that of the triceps and also a very short distance upon the adjacent inner surface of the scapula. It separates the origin of the coraco-olecranalis from the capsule and from the origin of the triceps. The latter expands somewhat into the capsule, and so separates this muscle behind from the capsule. With that exception it is in imme- diate contact with the capsule which is thin under it. It is inserted into the upper part of the humerus behind the pre- ceding, that is, just behind the ulnar edge between the coraco- hrachialis hrevis and the inner or third origin of the triceps. Indeed some of its fibres are continous with the fonner of those muscles in front, and with the latter behind. This muscle spreading itself to a greater extent upon the internal surface of the scapula in some animals becomes the sub^;ca])ular. It is called subscapular by Mivart in Meiiopoma and Menobranch. In the latter animal its extension upon the inner surface of the scapula is rather more decided than in Cryptobranch. 6. Coraco-olecranalis arises, by a tendinous band, from the edge of the coracoid, near the joint, internal to the middle of the preceding muscle, which separates it from the joint. It soon becomes muscular, descends the ulnar side of the arm dor- sally, joins the triceps and is inserted with it into the inner side of the olecranon. This coracoid accession to the triceps is common in Reptiles as well as in Urodelans. It results from the large relative size of the cora- coid, and reminds us of the accession which the quadriceps extensor cruris in these animals receives in the form of what I have called m- ternal rectus from the inner side of the front of the hip-joint. Only, in consequence of the difference in the rotation of the two limbs, the extensor of the foi'earm being directed backwards, gains its accession from the back of the shoulder-girdle, while the exten.sor of the leg being turned forwards gains its accession from the front of the pelvic girdle. The coraco-olecranalis is also an example of the deviation of a member of the flexor series to an extensor function : just as the biceps Jiexor cruris is an instance of the deviation of a member of the extensor sei'ies to the flexor function, the office in each instance being determined by the position and attachment.$