10 TOPOGEAPHICAL xVNATOMY OF 



the surface of the latissimus dorsi should be performed with some 

 degree of care, aiid note must be taken of a thin tendinous band that 

 passes within the humerus to end at the lesser tubercle of this bone. 



Cutaneous nerves from a variety of sources must also be noted. 

 Dorsal branches from the first few thoracic nerves appear in the intei- 

 scapular region, and sweep for a short distance over the scapular 

 muscles. In the region of the shoulder joint branches from the sixth 

 cervical nerve (n. supradavicularis) lie on the surface of the brachio- 

 cephalic muscle. Curving round the caudal border of the triceps 

 muscle and spreading out over its surface, are nerves derived from 

 the caudal pectoral with which branches from the second and third 

 intercostal nerves are connected. 



M. TRAPEZIUS. — The trapezius ^ muscle forms a thin, irregularly tri- 

 angular sheet over the scapular region, and extending well into the 

 neck. Two parts, a thoracic and a cervical, are to be distinguished. 



The cervical trapezius consists of fibres running in a caudal and 

 ventral direction, and some difficulty is experienced in clearing its 

 surface of a thin, closely adherent fibrous investment with strands 

 running at right angles to the fibres of the muscle. The origin of the 

 cervical trapezius is from the ligamentum nuchae from the level of the 

 epistropheus to the third thoracic vertebra, and its insertion is partly 

 into the spine of scapula and partly into the fascial aponeurosis that 

 covers the scapular muscles and is continued into the arm. 



The thoracic trapezius has a much more definite outline. From an 

 origin extending from the fourth to about the ninth thoracic spinous 

 processes (supraspinal ligament) the fibres of the muscle pass in a 

 cranial and ventral direction, to be inserted into the spine of the 

 scapula and more particularly into its tubercle. 



Dissection. — Cut through both parts of the trapezius muscle close to 

 their origin and turn them downwards. In doing so, seek for the dorsal 

 branch of the accessory nerve that travels down the neck to end in the 

 trapezius. 



This dissection exposes the rhomboid muscles. 



The surface of the latissimus dorsi should be cleaned. Considerable 

 care must be exercised when working over its broad, thin, and 

 aponeurotic tendon of origin. 



M. RHOMBOIDEUS CERViCALis. — The cervical rhomboid '^ muscle has its 

 origin from the cordlike part of the ligamentum nuchas from the level 

 of the epistropheus. The muscle is narrow and oblique in direction, 

 and its insertion is to the medial surface of the scapular cartilage, where 

 it is confused with the origin of the most cranial part of the ventral 

 serratus muscle. 



M. RHOMBOIDEUS THORACALis. — The thoracic rhomboid is .not clearly 



^ Trapezium [L.], from Tpairk^iov (trapezioii) [Gr.], a small table. From the 

 four-sided outline of the muscles of the two sides of the body taken together. 

 2 Rhombus [L.], fjofi/Sos (rhombos) [Gr.], a rhomb. elSos (eidos) [Gr.], form. 



