316 THE MUSCLES OF THE TRUNK. 



two or three lumbar vertebras being common to the two muscles. When those 

 slips and the tendons of origin from the lower lumbar spines are cut through 

 the inner surface of the muscle is brought into view, and it is then usually seen to 

 receive from two to four slender accessory tendons from the lower dorsal transverse 

 processes. The longissimus dorsi presents two series of insertions. The inner row 

 of insertions is a series of rounded tendons attached to the transverse processes of 

 all the dorsal, and the accessory processes of the lumbar vertebrae. The outer inser- 

 tions form a series of thin fleshy processes which are attached in the dorsal region to 

 the lowest nine or ten ribs, between their tuberosities and angles, and in the lumbar 

 region to the whole length of the transverse processes, and beyond these to the 

 lumbar fascia connected with them. 



e. The transversalis cervicis muscle prolongs upwards the column of fibres of 

 the longissimus dorsi. It arises from the transverse processes of the highest four or 

 five dorsal vertebrae, and occasionally the last cervical, and is inserted into the 

 posterior tubercles of the transverse processes of five cervical vertebrae, from the 

 second to the sixth inclusive. It generally receives a slip of the original fibres of 

 the longissimus dorsi. 



/. The trachelo -mast old muscle (transversalis capitis), which may be regarded 

 as the continuation of the longissimus dorsi to the head, arises in close connection 

 with the transversalis cervicis from the upper dorsal transverse processes, and also 

 from the articular processes of the lower three or four cervical vertebrae, and, forming 

 a thin flat muscle, passes to be inserted into the posterior margin of the mastoid 

 process, under cover of the splenius and sterno-mastoid muscles. It is usually crossed 

 by a tendinous intersection a little below its insertion. 



g. The spinalis dorsi is a long narrow muscle placed at the inner side of and 

 closely connected with the longissimus dorsi. It receives the slender tendinous 

 fasciculi from the lowest two or three dorsal spines, and other fleshy fibres spring 

 from the tendons which pass from the upper lumbar spines into the longissimus. 

 Its insertion takes place into a variable number, from four to nine, of the upper 

 dorsal spines, the slips being closely adherent to those of the subjacent semispinalis 

 muscle. 



Varieties. The slips of the longissimus dorsi arising 1 from the lower dorsal transverse 

 processes may be more independent than usual, forming- a small muscle with an insertion into 

 the transverse processes of the highest two or three dorsal vertebras the transversalis dorsi 

 of J. Miiller and Luschka. 



The spinalis cervicis is an inconstant muscle, arising' variably from the ligamentum 

 nuchae and the seventh cervical spine, or from one or two spines above or below this, and 

 inserted mainly into the spine of the axis, occasionally also into those of the third and fourth 

 cervical vertebras. 



The sacro-coccygeus posticus, or extensor coccygis, is a thin muscular slip occasionally, 

 although rarely, found extending from the lower end of the sacrum to the coccyx, and 

 representing the extensor of the caudal vertebras of the lower animals. (F. H. Jacobi r 

 " Beitrag zur Anatomic der Steissbeinmusculatur des Menschen," Arch. f. Anat., 1888.) 



COMPLEXUS AKD TRANSVERSO-SPINALES. The muscles of this group, comprising 

 the complexus, semispinalis, multifidus spihae, and rotatores dorsi, present the 

 feature in common of ascending with an inward inclination, and are thus dis- 

 tinguished from those last described. The most superficial, the complexus, has the 

 longest and most vertical fibres, but is the shortest in its whole extent, being limited 

 to the upper part of the dorsal and the cervical regions ; the muscle beneath it, the 

 semispinalis, occupies the greater part of both those regions ; the multifidus spinaa, 

 still more deeply placed, extends from the sacrum to the axis ; and the rotatores 

 dorsi, the deepest of all, are confined to the thoracic region. 



The complexus muscle (semispinalis capitis) arises by tendinous slips from the 

 transverse processes of the upper six or seven dorsal and the last cervical vertebras, 



