232 ANATOMICAL TECHNOLOGY. 



crosses obliquely the subjacent ectal lamina of the M. ectopectoralis 

 (Fig. 72, right side), and, at the junction of the proximal and middle 

 thirds of the brachium, is separated by only a slender line of con- 

 nective tissue from the cephalic division of the pecto-anteb?*ach ialis. 

 The cephalic border is the direct continuation of the caudal bor- 

 der of the clavo-trapezius, but is attached quite firmly to the strong 

 fascia covering the cephalic surface of the brachium. The muscle, 

 with the clavicle attached, may now be dissected up as far as the 

 ventral border of the antebrachium, but the distal half of the cau- 

 dal border cannot usually be separated from the pecto-antebracJii- 

 alis without cutting fibers. The examination of the insertion can 

 be made more easily after the removal of some other muscles. 



638. Origin. As stated under the clavo-trapezius ( 615), the 

 clavo-deltoideus, viewed from its ectal surface, is apparently the 

 direct continuation of that muscle ; the two are really separated 

 only by the transverse raphe, excepting that the ental layer of fibers 

 of the clavo-deltoideus arises from the ventral border of the clavicle 

 directly, or near its scapular end by short tendinous fibers. 



Insertion. At the ventral border of the antebrachium the 

 cephalic border of this muscle is firmly connected with the general 

 antebrachial fascia, and, at 8-10 mm. from the ulna, the muscle 

 joins the bracMalis to be inserted with it, by a flat tendon, upon a 

 rough and sometimes slightly depressed area on the caudal aspect 

 of the ulna, just distad of the greater sigmoid notch, and about 

 midway between the dorsal and ventral borders. See 693. 



Remark. By its origin this muscle seems to be a member of the deltoid group of 

 muscles, but its insertion associates it, functionally, with the flexors of the antebrachium. 

 When the clavicle is wholly absent, as with the horse, etc., the MM. clavo-deltoideus, clavo- 

 trapezius and davo-mastoideus seem to form a single muscle, the cephalo-humeralis. 



639. Explanation of Fig. 72. The pectoralis group of mus- 

 cles, partly dissected, seen from the ventral aspect. The neck is 

 toward the observer. The right and left of the figure correspond in 

 position with the right and left of the observer ( 56). 



Preparation. The cat is dorsicumbent, resting upon the right 

 side more than the left. The figure includes the thorax and caudal 

 part of the neck, together with the arms to a little distad of the 

 elbows. The arms are pulled away from the trunk so as to put the 

 pectoral muscles upon the stretch. On the right side, the borders 

 of the muscles have been defined by the removal of the fat and con- 



