BACK. 



373 



it as descendiiig from the neck to act on the ribs 

 and elevate them. 



The transversalis colli appears like a con- 

 tinuation of the longissimus dorsi, and as such 

 is often described. It arises along its internal 

 side by tendinous and fleshy slips from the 

 transverse processes of the second, third, 

 fourth, fifth, and sixth dorsal vertebra. These 

 unite, form a flat fleshy belly, which passes 

 upwards, outwards, and forwards, to be in- 

 serted by similar slips into the transverse pro- 

 cesses of the cervical vertebrae from the sixth 

 to the second inclusive, between the cervicalis 

 descendens and the complexus. The origin 

 and insertion of this muscle are connected only 

 to transverse processes hence the name. 



This muscle elevates the neck and inclines 

 it to one side. 



The trachelo-mastoideus lies to the inner side 

 of the transversalis colli, by which it is in 

 great measure concealed. It arises by ten- 

 dinous slips from the transverse processes of 

 two or three superior dorsal, and of three or 

 four cervical vertebrae. The slender muscle 

 enlarges as it ascends, passes a little outwards, 

 and is inserted into the posterior border of the 

 mastoid process, underneath the splenius ca- 

 pitis. Its inner side rests on the complexus, 

 then it covers the obliquus capitis inferior and 

 superior, and the origin of the digastric, also 

 the occipital artery. It is by some called the 

 complexus minor, from the resemblance it 

 bears to the complexus in its structure. Some 

 anatomists consider it as the cranial portion of 

 the longissimus dorsi and transversalis colli. 

 The origin of its name is obvious. 



When in action, this muscle extends the 

 neck, drawing the head back and to its own 

 side. 



The complexus is thicker and broader than 

 the muscles we have been now describing in 

 the cervical region. It arises from the trans- 

 verse and articulating processes of the four or 

 five superior dorsal vertebrae, and from the 

 transverse processes of the four inferior cervical, 

 by tendinous slips : these are followed by 

 fleshy and tendinous bundles. The muscle 

 thus formed passes upwards and inwards, to be 

 inserted into the os occipitis between its supe- 

 rior and inferior oblique ridges. The complexi 

 are close to each other above, separated only 

 by cellular tissue which is connected with the 

 ligamentum nuchae ; lower down, however, 

 there is some space between them. This mus- 

 cle is covered by the trapezius above, by the 

 splenii in the middle, and by the trachelo- 

 mastoideus and longissimus dorsi at its lowest 

 part. It rests on the spinalis colli, the obliqui 

 and recti capitis. The name is derived from 

 the complicated intermixture of tendinous and 

 fleshy fibres of which it is composed. A su- 

 perficial portion. of it is described by Albinus 

 as the biventer cervicis, but it does not usually 

 admit of subdivision. 



This muscle draws the head back on the 

 spinal column. 



In the muscles of this layer there are no 

 very striking differences to be observed in the 



other mammalia, nor in birds. Reptiles and 

 fishes differ too widely to allow of a com- 

 parison. 



Sixth layer. On raising the complexus and 

 trachelo-mastoideus we observe a beautiful 

 series of muscles for moving the head, viz. 

 the inferior oblique, the superior oblique, the 

 rectus capitis posticus major and Jidnor. These, 

 with the spinalis colli, form a six t It layer. 



The spinalis, or rather semi-spinalis colli, 

 arises by four or five fasciculi from the trans- 

 verse processes of as many superior dorsal 

 vertebrae; these unite, pass upwards and in- 

 wards, to be inserted into the second, third, 

 fourth, and fifth cervical spines, forming a 

 thicker muscle than the spinalis or semi-spinalis 

 dorsi. 



This muscle commences between the longis- 

 simus and semi-spinalis dorsi, then it lies be- 

 tween this last and the complexus. It is 

 almost concealed by the complexus. It ex- 

 tends the cervical vertebrae and inclines them 

 to its own side. 



The obliquus capitis inferior arises from the 

 spine of the second vertebra, passes outwards 

 and a little upwards and forwards, to be in- 

 serted into the transverse process of the first. 

 Its origin is connected with that of the rectus 

 posticus major, and the insertion of the spi- 

 nalis colli. Its insertion is blended with the 

 origin of the obliquus superior. It is fusi- 

 form in shape, the largest of the four muscles 

 to be met with here, and is often called ubli- 

 quus major. It covers the vertebral artery and 

 the lamina of the second vertebra, and is itself 

 covered by the complexus and trachelo-mas- 

 toideus, and by the posterior branch of the first 

 cervical nerve. 



It rotates the first vertebra on the second, 

 thus turning the face to its own side. 



The obliquus capitis superior (or minor} has 

 a pointed origin from the transverse process 

 of the atlas; runs upwards, inwards, and back- 

 wards, becoming broader, and is inserted into 

 the os occipitis between its transverse ridges, 

 just above the insertion of the rectus posticus 

 major. This muscle is covered by the splenius 

 capitis, trachelo-mastoideus and complexus. 

 It covers the vertebral artery and the interval 

 between the atlas and occiput. 



Its action is to extend the head, giving it 

 some inclination toils own side. 



The rectus capitis posticus major is triangu- 

 lar; its apex arises from the spine of the den- 

 t;ita; it passes upwards and a little outwards, to 

 be inserted by its base into the inferior transverse 

 ridge of the os occipitis. This muscle and its 

 fellow arise close together; passing up they 

 separate. The insertion is overlapped by that 

 of the superior oblique. The complexus covers 

 the greater part of it. 



This muscle draws back the head, turning 

 the face a little to its own side. 



The two obliqui, with this last muscle, en- 

 close a triangular space, in which we see the 

 posterior branch of the sub-occipital nerve 

 enveloped in adipose tissue, the vertebral 

 artery, the posterior half ring of the atlas, and 



