118 DISSECTION OP THE DOG 



of fibres running cranio-ventral in direction and converging upon the axilla, 

 where a tendon connects the cutaneous with the deep pectoral muscle. 



Two muscles, the brachio-cephalic and the sterno-cephalic, are more or 

 less blended, and together form a muscular sheet of no great thickness covering 

 the lateral and ventral aspects of the neck. 



M. BBAcmo-CEPHAUCTTS. — The brachio-cephalic muscle is divisible into 

 two parts, cleido-cervical and cleido-mastoid, joined together in the region 

 of the shoulder joint and continued to the arm as a single muscle. The place 

 of union of the two parts is marked by a transverse tendinous line, with which 

 the vestige of the clavicle is associated. 



The cleido-cervical muscle is attached to the occipital bone and the cranial 

 half of the ligamentum nuchae. 



The cleido-mastoid muscle, covered by the sterno-cephalic muscle, is 

 connected with the mastoid part of the temporal bone. 



It will be noted that the cleido-cervical and sterno-cephalic muscles in 

 the lateral and dorsal parts of the neck are in the same plane and practically 

 parts of the continuous thin muscular sheet ; whereas the cleido-mastoid 

 muscle is much thicker and in a deeper plane. 



The common aboral part of the brachio-cephalic muscle is inserted into 

 the crista tuberculi majoris of the humerus. 



M. sterno-cephalicus. — The sterno-cephalic muscle arises from the 

 manubrium of the sternum, and is inserted into the mastoid part of the 

 temporal bone. Its intimate connection with the cleido-cervical muscle 

 has just been noted. 



M. trapezius. — The trapezius muscle forms a thin irregularly triangular 

 sheet over the scapular region, and consists of two parts — cervical and thoracic. 



The cervical trapezius arises from the ligamentum nuchae caudal to the 

 attachment of the cleido-cervical muscle. It is also attached to the spinous 

 processes of the first two, three or four thoracic vertebrae. The fibres of the 

 muscle run in a caudal and ventral direction to be inserted into the spine of 

 the scapula. 



The thoracic trapezius consists of fibres which run in a cranial and ventral 

 direction. Their origin is from the spinous processes of the thoracic vertebrae 

 from the third or fourth to the ninth or tenth, and also from the lumbo-dorsal 

 fascia. The insertion of the muscle is to the dorsal third or so of the spine 

 of the scapula. 



Dissection. — Cut through the trapezius and cleido-cervical muscles close to 

 their dorsal attachments, and turn them downwards. In doing so, note 

 the presence of lymph-glands (lympho-glandulse cervicales profundae) 

 between the two muscles and under cover of the cleido-cervical and 

 omo-transverse muscles. In the same neighbourhood, the superficial 

 cervical branches of the transverse scapular vessels and the accessory 



