PECTORALIS GROUP. 235 



Triceps (§§ 687-689). — The caudal or ectal aspect of tl;e entotriceps appears on both 

 sides, but the divisions are not defined. 



Xiphi-huineralu (§ 660). — On the right the sternal part is shown but not named. On 

 the left, its course entad of the entapectoralis is indicated by the broken lines, and part of 

 its humeral end is seen. Usually tliis muscle is more intimately connected with the 

 xiphisternum. 



PECTORALIS GROUP. 



§ 640. General Remark. — The two pectoral muscles of man, 

 ectopectoralis^ " pectoralis major," and entopectoralls^ "pectoralis 

 minor," are represented in the cat by several muscles to which 

 Straus-Durckheim and others have applied distinct names. Most 

 of these divisions, however, may be recognized as i)arts of two 

 masses, an ectal or superficial., arising nearer the cephalic end of 

 the sternum, and extending laterad to the dlapTiysis of the hume- 

 rus, and an ental or deep., arising ft-om the caudal part of the ster- 

 num, and extending later o-cepTialad to the liead of the bone. The 

 former, representing the ectopectoralis, tends to subdivide into 

 superposed laniiiKB ; the latter, representing the entop>ectoraUs, 

 tends rather toward a division into parallel fasciculi. See § 572, 

 Humphrey, E, 110, and Wilder, 20, 306. 



§ 641. Crosifiiig of the Pectoral Elements. — Excluding the M. pecto-antebrachialis, 

 whicji is inserted upon the antebrachium, the pectoral mass may be roughly described as 

 a series of four superposed laminae crossing one another in such a way that tlie cephalic in 

 origin, is didal in insertion, while the caudal in origin \s proximal in insertion. 



The ectal lamina of the M. ectopectoralis (Fig. 72) arises from the prcTesternum and ceph- 

 alad of it, and is inserted upon the middle third of the humerus. The ental lamina, as a 

 whole, arises from the cephalic third of the sternum, and is inserted upon the proximal 

 three fifths. The M. e7itopectoralis, as a whole, arises from the entire mesosternum, and is 

 inserted upon the proximal third. Finally, the Jf. xiphi-humeralis arises from or near the 

 xiphisternum, and is inserted upon the head and neck of the humerus. 



It follows from this arrangement that the general direction of the fibers of the first por- 

 tion is nearly transverse ; that, in the natural attitude of the arm, for a part of their course 

 at least, the fibers of the last portion run nearly parallel with the meson ; while the direc- 

 tions of the other two portions are intermediate. 



A somewhat similar relation exists between the less distinctly separable regions of the 

 human ectopectoralis as described by Gray (A, 400) and Quain (A, I, 193). 



The insertion lines of the two laminae of the ectopectoralis are nearly parallel, but 

 almost meet at their distal ends (Fig. 69). If they were continuous, they might be de- 

 scribed as a single line folded upon itself, and their tendons would be strictly comparable 

 with the tendon of the human pecturaUs major as described by Gray and Quain. 



§ 642. The Pectoral Complexity. — In the cat there may be recognized eight or nine 

 elements of the pectoral mass, more or less independent as to origin or insertion or both. 

 In man, the M. entopcctoralis {P. minor) is distinct, and the M. ectopectoralis is more or 

 less readily in different subjects separable into two or three portions, whose origins and 

 insertions, however, are nearly or quite continuous. 



It may be said, therefore, that the provision for separate and independent movement 



