OF DIDELPIIYS VIRGINIANA. 101 



The innermost, or most lateral of these, seems to represent a series of "intertransversa- 

 les," lying between and upon the large "transverse processes," separating the psoas from 

 the quadratus lumhorum. It takes origin from the ilium, below and inside the apex, and 

 proceeds upward to the eleventh — twelfth rib, thus entering the thorax, past the dia- 

 phragm, and there lying upon the anterior surfaces of the bodies of the vertebrae. 



The next three bundles occupy the broad, shallow fossa between the transverse and artic- 

 ular processes. The largest and most lateral of these is the quadratus lumhorum, begin- 

 ning at the apex of the ilium, and proceeding to the last rib. It is wholly muscular, and 

 incompletel}^ divisible into several layers of fasciculi ; and blends above with the sacro- 

 lumbalis. The latter, and the longissimus dorsi — both to be presently noticed in more 

 detail — together form the third bundle, and constitute the "erector spina3." The fourth 

 bundle is the very distinct, terete belly of origin of a caudal extensor, described below. 



The fifth bundle occupies the narrow deep fossa between the articular and spinous pro- 

 cesses, representing a "multifidus spinoe." Below, it runs uninterruptedly into the tail. It 

 consists of a series of little oblique fascicles, filling the groove, arising fleshy from articular 

 processes, and inserted tendinous into spinous processes, two or three vertebra3 above. At 

 the last dorsal its bed becomes very narrow and the muscle is proportionally diminished In 

 size. It again enlarges, however, and continues upward, with much the same characters, 

 but intimately blended with the spinales dorsi and colli. 



The erector spinse in the lumbar region consists mainly of a sei'ies of flattened tendons 

 that take origin from the apices of the spinous processes, and blend into a strong fibrous 

 layer that invests the subjacent muscle, and is continued as a strong fliscia down over the 

 sacrum. Laterally, and toward the thorax, however, the sacro-lumbalis part becomes a stout 

 fleshy mass that blends with the quadratus, and is then continued upon and inserted into 

 the last two or three ribs, at a little distance from the spine. 



The upward prolongation of the saci-o-lumbalis — the "musculus accessorius" — is perfectly 

 distinct from the longissimus. It is a flat, narrow, sub-prismatic strip lying along the outer 

 border of the latter, just behind the origins of the serrati, an inch or more from the spine. 

 It consists of a series of slips arising fleshy from the ribs, and inserted tendinous into the 

 second or third rib above. The several tendons are tolerably distinct, but the muscular 

 parts are completely blended. 



Tliis muscle, properly speaking, ends at the first rib. To its outer side, and partially 

 blended with it, a slip arises from the third — first rib, and is inserted into the transverse 

 process of the seventh cervical. This is the "cervicalis ascendens." 



The erector spinaj, after disengaging the sacro-lumbalis, continues upward upon the spine, 

 overlying the multifidus, and more immediately the spinalis, as the longissimus doi'si. The 

 latter is distinct from the sacro-lumbalis, but inextricably blended with the spinalis. The 

 longissimus and spinalis together fill the groove between the ribs and the apices of the 

 spinous processes ; the former nearest the median line, the latter more external. Together 

 they consist of a series of long, stout, flattened tendons, arising from the apices of the 

 spinous processes, and continually giving off numerous fleshy slips that are inserted into 

 the articular and transverse processes of the vertebrae, and angles of the ribs. The two 

 muscles, hitherto confused, separate opposite the fourth or fifth dorsal — the origin of the 

 biventer cervicis intervening. The longissimus passes outside the biventer, complexus and 

 trachelo-mastoideus, separating the latter from the cervicalis ascendens, and continues up 



MEMOIRS B09T. 80C. NAT. HIST. Vol.. II. 26 



