DISSECTION OF THE DOG 153 



M. longissimus cervicis. — This muscle is immediately ventral to the 

 splenitis, and intimately connected with the longissimus dorsi. With an 

 origin from the transverse processes of the first five or six thoracic vertebrae, its 

 insertion is into the transverse processes of the last four or five cervical vertebrae. 



Dissection. — Reflect the splenius by cutting through the entire length of 

 its origin. Observe the branches of the cervical nerves. Then reflect 

 the longissimus cervicis by a transverse incision about the middle of the 

 muscle. 



M. longissimus capitis et atlantis. — These two muscles are readily 

 separated, but are better considered together. The longissimus capitis muscle 

 arises from the transverse processes of three or four thoracic vertebrae and 

 from the last three or four cervical articular processes. By union with the 

 splenius the muscle obtains an insertion into the mastoid part of the temporal 

 bone. 



The longissimus atlantis is a very much smaller muscle than the preceding, 

 and passes from the third, fourth, fifth, and sixth cervical articular processes 

 to the wing of the atlas. 



M. semispinals capitis. — Dorsal and medial to the preceding in position, 

 the semispinalis muscle of the head consists of two parts — -m. biventer cervicis 

 and m. complexus. The former is readily distinguished by the presence of four 

 oblique tendinous intersections. This muscle arises from the spinous processes 

 of the second to the fourth or fifth, and from the transverse processes of the 

 fourth, fifth, and sixth thoracic vertebrae, as well as from the ligamentumnuchae. 

 The complexus muscle has its origin from the transverse processes of the first 

 two or three thoracic vertebrae, and from the articular processes of the last five 

 cervical vertebrae. 



The two parts of the semispinalis muscle may or may not join about the 

 level of the atlas. In any case they are inserted into the occipital bone. 



Two branches of the second cervical nerve are associated with the biventer 

 cervicis muscle. A large branch pierces the muscle close to its insertion and 

 proceeds to the ear. A much smaller nerve either pierces the muscle close 

 to the middle line, or appears between the muscle and the ligamentum nuchae, 

 and ramifies in the skin medial to the base of the ear. 



Dissection. — Cut across the complexus muscle on a level Avith the joint 

 between the atlas and the epistropheus. Free the biventer cervicis muscle 

 from its origin and turn it towards the head. In reflecting these two 

 muscles the large dorsal primary divisions of the cervical nerves will be 

 observed between the complexus and multifidus muscles. 



M. semispinalis dorsi et cervicis. — This muscle, as has previously 

 been noted, is continuous with the longissimus dorsi. It receives a bundle of 



