BICIPITAL ARCH. 245 



ARCUS BICIPITALIS— THE BICIPITAL ARCH (Fig. 73). 



§ 663. This name is given to the tendinous arch through which 

 passes the M. biceps (Fig. 73, 75). In man, normally, the edopecto- 

 ralis passes ectad of the Weeps, while entad of it pass the tendons of 

 the latissimus and teres. In the cat, as in the Mammals generally, 

 there is a union of the ental with the ectal muscles so as to form a 

 complete arch over the Mceps. The ectal, or cephalic, pillar of the 

 arch is formed by the caudal division of the entopectoralis ; the 

 ental, or caudal, pillar, by the teres and latissimus, while the 

 xipM-humeralis and dermo-humeralis are connected with one or the 

 other pillar, with the muscles composing them, or with the convex- 

 ity of the arch itself. 



Explanation of Fig. 73. — The ental aspect of the muscles about 

 the left shoulder, and the ectal aspect of the MM. serratus magnus 

 and levator anguli scapulce. 



Frepeiration. — After the dissection and reflection or removal of 

 the muscles of the trapezius and pectoralis groups, and of the other 

 muscles already described as connecting the soma with the arm and 

 shoulder girdle, the arm and scapula were turned dorsad. 



Certain muscles (scaleni) not described herein have been wholly 

 removed from the neck and cephalic part of the thorax, and of the 

 M. ectobliquus (abdominis) there is left little more than the first six 

 digitations. There are thus exposed the M. rectus with its wide, 

 thin tendon, and parts of the costal cartilages 7-8, with the inter- 

 vening MM. inter costales. 



Bones, etc. — Areus bkipitalis, witli its cephalic and caudal pillars (Clm. cepJialiea and 

 eaudaHs)—The bicipital arch (§ 663).— This is seen to embrace the M. biceps. There is 

 considerable variety in the mutual relations of its constituents. In the preparation fig- 

 ured, the M. latissimus might be said to enter into the composition of both pillars, and the 

 M. dermo-humeralis does not directly reach the arch at all. 



Costa and cartilago (§§ 441, 443).— The first rib is exposed and the name is written 

 thereon. The sternal ends of the eighth, ninth and tenth ribs are seen near the cut bor- 

 der of the M. eetdbUquus. The first costicartilage affords insertion to the tendon of the M. 

 rectus, and parts of the seventh to the tenth appear between the margins of the MM. rectus 

 and ectobliquus ; elsewhere their position is indicated by dotted lines. 



Biapophyses cermcales — The transverse processes of the cervical vertebrae (§ 481). — 

 These are numbered 1-7, but no name has been written near them. Note the gradual 

 increase in the extent of their bifurcation toward the caudal end of the series. 



Pre. {Processus) coracoideus — The coracoid process of the scapula (Fig. 43, 44, 4S A ; 

 §§ 389, 400). 



