210 HISTORY OF THE HUMAN BODY 



IV. TRANSVERSO-SPINALIS SYSTEM. This is a complex sys- 

 tem, the elements of which arise from transverse processes and 

 insert upon the spinous processes of vertebrae situated more 

 anteriorly. It is in close contact with the previous system, by 

 which it is covered, and may be imperfectly divided into three 

 series or layers, superficial, middle and deep, called respectively 

 semi-spinalis, multifidus and rotatores. These layers differ 

 not merely in position, but in the course of their separate slips, 

 since those of the first pass over 4-6 vertebrae between origin 

 and insertion, those of the second pass over 2-3, while those 

 of the deep layers are themselves subdivided into two series, 

 rotatores longi et breves, of which the outer pass over a single 

 vertebra, while the inner attach to adjacent vertebrae. 



The semi-spinalis is divisible into three portions, dorsi, 

 cervicis and capitis. The last of these, semi-spinalis capitis, is 

 a large and well-developed muscle, divided longitudinally into 

 a median and a lateral bundle; the inner one of these is tra- 

 versed by a myocomma, dividing the muscle into two fleshy 

 bellies, from which comes the older name of biventer cervicis. 

 The outer portion forms the complexus (major) of the older 

 anatomists. 



V. INTERVERTEBRAL SYSTEM. Still beneath the multifidus 

 and rotatores are several series of short muscles, stretching be- 

 tween adjacent vertebrae, and probably representing a few 

 fibers of the primitive myotomes, which have remained in their 

 original condition. Of these the most extensive are the inter- 

 spinales, lying on either side of the median line, and extend- 

 ing between adjacent spinous processes. Typically associated 

 with all the intervertebral intervals, they occur in man mainly 

 in the cervical and lumbar regions, including the first and last 

 of the dorsal vertebrae, and are wanting through the middle 

 of the back. A second set, the intertransversarii, between ad- 

 jacent transverse processes, occur in lumbar and cervical 

 regions, but in the thoracic are represented by tendons without 

 contractile fibers. The intertransversarii of the lumbar region 

 are divided into medial and lateral portions, a division probably 

 without morphological significance ; on the other hand, those of 



