PECTORALIS GROUP. 235 



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

 sides, but the divisions are not defined. 



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

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

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

 xiphisternum. 



PECTORALIS GROUP. 



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

 ectopectoralis, " pectoralis major," and entopectoralis, "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 parts of two 

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

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

 rus, and an ental or deep, arising from the caudal part of the ster- 

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

 former, representing the ectopectoralis, tends to subdivide into 

 superposed lamince ; the latter, representing the entopectoralis, 

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

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



§ 641. Crossing of the Pectoral Elements. — Excluding the M. pecto-antebraehialis, 

 which 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 the cephalic in 

 origin is distal in insertion, while the caudal in origin, is proximal in insertion. 



The ectal lamina of the M. ectopectoralis (Fig. 72) arises from the praesternum 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. entopectoralis, as a whole, arises from the entire mesosternum, and is 

 inserted upon the proximal third. Finally, the M. 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, 1, 193). 



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

 almost meet at their distal ends (Pig. 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 pectoralis major as described by Gray and Quain. 



§ 643. T/ie 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. entopectoralis (P. minor) is distinct, and the J/, 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 



