Licence: Public Domain Mark
Credit: On the muscles of the back / by Holmes Coote. 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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![llie necessity of preserving a firm column of support, upon wliich the ribs may move,) scarce any extension is possible between the superior vertebraj, the in- ters])iualis muscles are represented by ligamentous bands passing from the imbricated spinous processes; and the common extensor pulls upon them as upon a single piece. The oblique direc- tion of the cervical articulating process allows of considerable rotation com- bined with extension: thetongue of bone, dipping down from the anterior inferior margin of the body of the cervical vertebra, presents flexion forwards. In a well-marked skeleton, the apex of the spinous process of the axis may be made in extreme extension to touch the apex of the seventh cer^dcal vertebra, tlie intervening shorter spines radiating from the point of contact as from a centre. Tlie articulating processes in the dorsal region allow of the lateral swaying movement of the trunk. Rota- tion is very limited, and extension of the vertebrae one upon the other is im- possible in the upper part of the chest from the oblique imbricated direction of the spinous processes. At the junc- tion of the lumbar and dorsal regions we have combined both the lateral swaying movement, and also flexion and extension, as is well illustrated by the springing movement in any of the active carnivoi'ous quadrupeds. The mobility of the vertebral segments, which ceases at the sacrum, is in a slight degree resumed in the coccyx, which possesses the power through the coccygeus muscle of curving forwai’ds to diminisl) the inferior outlet of the pelvis. With these prefatory remarks 1 shall now pass to the anatomy of the muscles of the back, purposely rendering their description as concise ns possible. The muscles first exposed ujion the reflection of tlie integument of the back, belong to tlie upper extremity, which we are taught by homology to regard as the separated and displaced costal appen- dage of the occipital vertebra. The trapezius, highly developed, still retains at the iqiper extremity its attachment to the occipital spine. The levator anguli scapulae and the serratus mngnus, jior- tions of the same muscle, extend from the ribs to the scapula; a bone, wbich although triangular and expanded for muscular attachment, is now recognised as a rib. The latissimus dorsi and the two rhomboids arise from the spines of the vertebrae, and are inserted resjiec- tively into the humerus and the scapula. Were we to represent the muscular system of a vertebrate animal in its simplest fonn. it would be expressed as muscular and tendinous slips passing from contiguous vertebrae. Yet here we have the separated costa or rib of tbe occiput receiving muscular fibres from nearly the whole length of the vertebral column. The vertebral apo- neurosis, which extends from the upper- border of the seiTatus ])osticus inferior, under the serratus posticus superior, to the splenius muscle, bends down the proper muscles of the back. They may be arranged in three layers : I, oblique; 2, longitudinal; and 3, oblique. 1st Layer.— Oblique, from within upwards arrd outwards. The splenius muscle occupies the cervical region, where rotation is more free than in other- parts of the trunk. It arises from the foin-or five upper dor-sal, and the four or five lower cervical spines; the fibres pass upwai-ds and outwards to be inserted into tbe posterior tubercles of tbe ti-ansverse jrrocesses of the three or four upper cervical vertebrae, into the mastoid pr-ocess and into the superior curved ridge of the occipital bone, or, homologically expressed, irrto the diapo- physes of the par-ietal and occipital, arrd three or four upper- cervical vertebi-ae. 2nd L\YErr.—Longitudinal, composed of three muscles: interspinales, longis- simus dorsi, sacro-lumbalis. Tbe inter-spinales exist as well-marked mrrscles in the cervical and ujrper lum- bar regiotr: irr the for-mer they are ar-ranged in pairs, the sjiiuous processes being bifid. Jrr the upper dorsal region they are represented by tendirrous bands jrassing between the imbricated dor-sal spines. In the lower lumbar r-egion they cease to exist as rrurscles, the quadrilateral spines adnrittiug no exten- sion backwards. They cease irr the sacrum, where the ver-tebrae coalesce to form a single piece, and they then become blended with the muscular arrd fibr-ous tissues covering tbe posterior- surface of that borre. But at the junc- tion of the lutubar and dorsal regions there exists an hypertrophy of the inter- spinales. At that point, where great freedom of movenrent is allowed by the difler-errt directions of the articulatiirg processes, which look backwards and](https://iiif.wellcomecollection.org/image/b22424702_0005.jp2/full/800%2C/0/default.jpg)
