SCHULTE, SE1 WHALE. 42!) 



aponeurosis, which covers its surface. This is especially conspicuous in the thorax and 

 neck, where a considerable portion of the muscle along its ventro-lateral margin is derived 

 from this source. The iliocostalis begins as a series of tendons derived from the ventrolateral 

 margin of the longissimus. The first of these leaves the tendon of origin of the latter at the 

 junction of the pedicle with the flukes. Ten such tendons in all were present, increasing in size 

 to the middle of the pedicle and then diminishing. The fourth, fifth and sixth are the largest. 

 These all pierce the septum which separates the longissimus and iliocostalis. In addition the 

 muscle receives slips from the accessory processes. The fasciculi are directed nearly longitudi- 

 nally, but with a slight deviation laterad and ventrad, to their insertions by mixed tendinous 

 and fleshy fibres into the transverse processes of the lumbar, thoracic and cervical vertebrae 

 (iliocostalis) , and into a vertical line upon the exoccipital between the trachelo-occipital muscle 

 mesad and the obliquus superior laterad (longissimus). In the thoracic region slips are also 

 attached to the ribs mesal to their angles and to the insertions of the trans versarius. 



The transverso-spinalis consists of fasciculi extending from the transverse processes to the 

 spines of the vertebra; with a general direction rostro-mesad. It may be resolved into a super- 

 ficial portion (semispinalis) and a deep portion, multifidus, though many fasciculi extend from 

 one to the other. In the pedicle where the whole system is of small size and for the most part 

 under cover of the longissimus, from which it is but imperfectly separate, I was obliged to give 

 over the attempt to analyze its components. As the thorax is approached the semispinalis 

 increases in size and attains considerable depth, gradually making its appearance between the 

 spines and the longissimus. Its fasciculi arising from accessory processes are inserted into 

 the spines of more rostral vertebrae. The fasciculi have a very oblique course and pass over 

 several vertebrae from origin to insertion. From about the mid-dorsal region the insertion into 

 spines ceases, indeed a few fasciculi now arise from this source, and the origin from the accessory 

 processes enlarges spreading on to the bases of the transverse processes. The muscle becomes 

 very bulky rising high above the level of the spines as it approaches its insertion into a large 

 area on the supraoccipital, between the midline and the attachment of the longissimus. This 

 portion is the semispinalis capitis and constitutes by far the major part of the whole system. 

 From its deep surface, in the upper thoracic and cervical region, several large bundles are given 

 to the underlying multifidus. The semispinalis cervicis, rectus capitis posticus, obliquus and 

 multifidus are exposed on its reflection. 



The semispinalis cervicis is a small muscle arising from the transverse processes of the lower 

 cervical and the first three thoracic vertebrae. It is directed obliquely rostro-mesad and inserts 

 upon the arches of the epistropheus and atlas, many of its fasciculi passing uninterruptedly into 

 the rectus capitis posticus. 



The multifidus is composed of bundles passing between spines and transverse processes. 

 In the upper lumbar region they have a moderate obliquity passing over three or four vertebrae 

 in their course from origin to insertion. In the thorax their course becomes more longitudinal 

 and some of the superficial bundles are of reversed obliquity passing from thoracic spines to 

 cervical transverse processes. As a whole this system is of small size filling the interval between 

 accessory and spinous processes. Caudad it resisted my efforts to separate it from the semi- 

 spinalis, rostrad while more independent it yet receives several slips from the deep surface of 

 that muscle. I did not examine the submultifidus. Interspinales are present, paired and of 

 moderate development. 



The rectus capitis posticus I could not resolve into major and minor. It arises broadly from 



