164 COUES ON THE OSTEOLOGY 



The muscles moving the caudal extremity of the spine, do not present any special 

 peculiarities, with the exception of the cruro-coccygcus, or " femoro-coccygeus." This, from its 

 origin and relations, may be more conveniently considered in connection with the muscles 

 of the posterior extremities. 



Of the abdominal muscles, the obliquiis externus vel descendcns is particularly remarkable for 

 its extensive origin, which causes it to form an investment, not only of the abdominal, but 

 also of the greater part of the lateral thoracic parietes. It arises by broad aponeurotic 

 digitations from the retrocedent processes of about seven ribs ; from the margins of the 

 ilium ; from the horizontal ramus of the pubis ; and from the posterior margin of the 

 sternum, overlying a great part of the broad xiphoid cartilage ; its fibres (as usual in the 

 class) are directed inwards, with but a moderate inclination downwards ; and continue 

 carneous almost to the median raphe, there being but a short aponeurosis before the inser- 

 tion into the " linea alba." 



Muscles of the Upper Extremities. 



Pectorales. A remarkable peculiarity of the great pectorals is that they are united with 

 each other by an extensive band of transverse fibres which pass across from one to the 

 other just anterior to the keel of the sternum, lying upon the clavicular symphysis, and 

 covering these bones for an inch or more. 



The fleshy mass commonly called the " pectoralis major" consists of three portions, so 

 very distinct from each other, in their origins and insertions, as well as in the motion they 

 impress upon the humerus, that I prefer to consider them as distinct muscles. They are 

 more distinct than the three gluten of the human subject. 



The first pectoral, or "pectoralis maximus" is large, long, and broad, but very flat, and not 

 thick. It arises from the whole of the clavicle ; from the lower half of the fibrous septum 

 which stretches vertically above it; from the side of the keel of the sternum (except that 

 part occupied by the succeeding) ; and from the edge of the sternum all around, as high as 

 the articulation of the last sternal rib. The mass laterally overlaps the edges of the bone; 

 posteriorly is continuous with the fibres of the abdominal muscles. In the middle of the 

 muscle is a broad longitudinal tendinous septum, which divides the mass into a greater por- 

 tion, with origins as above, and a smaller part, which arises from an oblique ridge upon the 

 face of the sternum. The fibres converge without twisting to the ordinary insertion. 



Pectoralis medius. Arises from the inner half of the anterior third of the keel of the ster- 

 num (all that portion not occupied by the preceding) ; from the sternum itself as far as an 

 oblique ridge which runs from the sterno-coracoid articulation to the keel, and separates 

 this muscle from the next ; and from the upper half of the supra-clavicular fascia. Its 

 fibres converge to joass under a large trochlear surface of the coracoideum (converted into 

 a foramen by the apposed clavicle) to their insertion by a stout rounded tendon into the 

 ridge of the humerus near its extremity. 



It is a powerful external rotator of the humerus ; and its further action elevates the 

 humerus directly from the back, carrying its distal extremity in the arc of a vertical circle 

 toward the head. 



Pectoralis minimus. Situated posterior and just external to the preceding, this muscle 

 arises from the outer half of the broad base of the coracoideum, and the contiguous por- 

 tions of the sternum. It is much smaller than the preceding, with the posterior border of 



