230 ANATOMICAL TECBNOLOOT. 



border of the scapula along a dorso-ventral line from the 5th tho- 

 racic neural spine. 



Transect the muscle along a line between the 7th rib and the 

 vertebral border of the scapula, beginning at the caudo-ventral 

 border and alternately lifting and dividing the successive parts. 

 Toward the meson, along a line extending ventro-caudad from the 

 10th, 11th or 13th thoracic spine to the lateral border of the verte- 

 bral muscles, about 3 cm. from the meson, the muscular sheet gives 

 place to a strong fascia. 



In reflecting the brachial portion of the muscle, note the attach- 

 ment of the dermo-humeralis to its ectal surface (Fig. 74), its close 

 relations with the subjacent M. xipM-Tiumeralis, and the presence 

 of a lymphatic gland near the dorso-caudal border of the latter. 

 Turn the arm so as to bring the convexity of the elbow dorsad, and 

 thus expose the space between the brachium and the scapula, and 

 note that the ental surface of the latissimus is joined, near its 

 cephalic border, by a thick muscle, the teres (Fig. 75), from the 

 glenoid border of the scapula, and that, from the ectal surface, close 

 to the attachment of the dermo-humeralis, there proceeds distad a 

 muscle, the epitrochlearis (Fig. 75). 



The details of the connection of the latissimus with the humerus 

 and the bicipital arch are more easily examined after the dissection 

 of the pectoralis group, and the removal of the arm from the body. 



§ 636. Origin. — In two parts : (A) by muscular or short tendi- 

 nous fibers from the sides of the tips of the thoracic spines from the 

 4th or 5th to the 10th inclusive, and from the corresponding inter- 

 spinous ligaments ; this part of the origin is wholly covered by the 

 origin of the spino-trapezius ; (B) from the dorsimeson, between 

 the 10th thoracic spine and the sacrum, by a strong triangular ten- 

 don, the lateral angle of which corresponds nearly with the lateral 

 border of the vertebral mass of muscles. 



Insertion. — At the junction of the 2d and 3d fourths of the hu- 

 merus, upon its ventral aspect, by a thick tendon which forms the 

 caudal pillar of the bicipital arch. 



The detailed description of the insertion must include that of the 

 M. teres (§ 680, Fig. 75) ; but though the tendons of the two muscles 

 are inseparably united, there are indications of the manner of their 

 junction. The joint tendon, at a point midway between the hume- 

 ral end and the point of separation of the two muscles, is wholly 

 tendinous as to the distal fifth of the caudal surface which seems to 



