File:Image from page 263 of "On the anatomy of vertebrates (electronic resource)" (1866) (14752362051).jpg

Identifier: b20416039_001 Title: On the anatomy of vertebrates [electronic resource] Year: 1866 (1860s) Authors: Owen, Richard, 1804-1892 Subjects: Anatomy, Comparative Vertebrates Fishes Reptiles Mammals Birds Publisher: London : Longmans, Green Contributing Library: Wellcome Library Digitizing Sponsor: Wellcome Library

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Text Appearing Before Image: and specialisation of the segments of thelimbs the muscles became larger, more numerous, and more dis-tinct. The pectoralis, fig. 141, \m, 16, has its origin extended fromthe fore part of the coracoid and episternum to the linea alba, oraponeurotic continuation of the sternum, half an inch beyond thecoracoid; the fibres converge to their insertion into the pectoralridge of the humerus; but so that the coracoid portion is almosta distinct muscle. This muscle suspends the fore part of thetrunk upon the fore-legs, and besides depressing the humerus,rotates it in the plane of the bodys axis as different portions ofthe muscle come into action. A muscle, fig. 140, 11, arising from scattered fibres by a longi-tudinal tract of the aponeurosis, covering the longissimus andspinalis dorsi, collects those fibres and contracts as it descendsover the hind part of the scapula to be inserted into the back partof the pectoral ridge. An anterior parta ib. 22, of the same 218 ANATOMY OF VERTEBRATES.141

Text Appearing After Image: Miudcs of iNilaiiiaiHlr.i i.crrestris. clxxxvii system of converging fibrestakes its origin from thescapula itself, and convergesto an insertion close to thatof the preceding. The entiremass of the muscles 22 and11 antagonise that, 16, 16#,below ; one raises, the otherdepresses, and both rotate,the humerus to and fro. Asthe fore-limb gains size andpower in higher air-breathers,the muscle 11 seeks a moreextended origin, covers agreater proportion of the seg-mental system of trunk-muscles, acquires the nameof latissimus dorsi, and, inAnthropotomy, is classedamongst the 4 first layer ofthe muscles of the back. Themuscle 22, becomes deve-loped into e supra- and 4 in-fraspinatus? and, perhaps,also deltoides. The pro-tractor scapidce, arising, as inFishes, from the paroccipital,now also derives fibres fromthe transverse processes of thefirst and second trunk-verte-bras, and divides into two dis-tinct fasciculi; one, fig. 140, 19, is inserted into the baseof the scapula; the other, ib. 20, i

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