MUSCLES OF THE TRUNK. 197 



Man, and the trachelo-acromialis peculiar to quadruped mammals 1 G. Cuvier, ( Lemons 

 d'Anatumie Comparee,' 2nd edition. (This is the muscle which Percivall names the 

 levator humeri. The above is the designation given to it by Girard and Chauveau. 

 Leyh gives it the same designation as Bourgelat.) 



Extent Situation Direction Composition. This muscle extends from 

 the summit of the head to the inferior part of the arm, and is applied to the 

 scapulo-humeral angle at the side of the neck, in an oblique direction down- 

 wards and backwards. It is composed of two portions lying longitudi- 

 nally and somewhat intimately united, and distinguished into anterior and 

 posterior. 



Form Structure Attachments. A. The anterior or superficial portion 

 (Fig. 106, 6) constitutes a long fleshy band, which appears to be united, by 

 its anterior border, to the cuticular muscle of the neck. Its superior 

 extremity, thin and wide, is attached to the mastoid process and crest by an 

 aponeurosis (Fig. 102, 7), which is united, in front, to the tendon of the 

 sterno-maxillaris by a very thin cellulo-aponeurotic fascia. Its inferior ex- 

 tremity, thicker than the superior, is inserted by means of a very short 

 aponeurosis into the humerus, on the salient border descending from the 

 deltoid imprint, and which limits, in front, the furrow of torsion on the 

 body of that bone (Fig. 102, 7). 



B. The posterior or deep portion (Fig. 102, 9) is a second muscular band, 

 shorter anrl stronger than the preceding. It is attached, above, to the 

 transverse procasses of the first four cervical vertebras by as many fleshy bands 

 (Fig. 102, 8'), which cover the superficial portion. The upper digitation, 

 given off to tno atlas, is united to the tendon common to the small complexus 

 and splenius (Figs. 105, 9 ; 106, 9', 10, 11). The inferior extremity of this 

 portion of the muscle widens on the scapulo-Tiumeral angle, which it 

 envelops in becoming closely united to the anterior portion, terminating 

 with it on the humerus. An aponeurosis, which is confounded with that of 

 the trapezius, and sends off a septum into the interstice between the two 

 portions of the long abductor of the arm, concurs to fix this extremity by 

 spreading over the muscles of the arm. 



Relations. It is covered, near its mastoid insertion, by the parotid gland 

 and the cervico-auricularis muscles ; for the remainder of its extent, by the 

 aponeurosis of the cuticularis colli, from which it is separated by a thin 

 fascia continuous with that which extends over the trapezius. It covers the 

 splenius, the small complexus, the oblique muscles of the head, subscapulo-t 

 hyoideus (to which it adheres intimately), the digastricus, long flexor of the 

 head, the angularis, scalenus, small pectoral, supra- and infraspinatus, the 

 long abductor of the arm, and the coraco-radialis. 



1 At first sight we might hesitate to admit that this muscle is formed of such varied 

 and complicated elements as are enumerated above. Nevertheless, it is a scientific fact ; 

 and we will give a demonstration, as simple as it is clear, that such is the case the 

 idea we owe to J. F. Meckel. If we take the Dog, for example, and suppose it to be 

 possessed of a clavicle extending from the anterior extremity of the sternum to the 

 acromion ; this clavicle would cut, transversely, the inferior portion of the mastoido- 

 humeralis, which would thus be divided into two portions, a superior and an inferior. 

 The first, extending from the clavicle to the mastoid process, on this side, and on the 

 other to the mastoid crest, as well as to the cervical ligament, where it is confounded with 

 the trapezius, would exactly represent the clavicular portion of the latter muscle, and 

 the cleidn-mastoideus. With resv.ect to the interior portion, it perfectly resembles, by its 

 attachments, the clavicular portion of the deltoid. But, on the contrary, if we suppose 

 Man deprived of a clavicle, the three muscular fasciculi indicated, in becoming con- 

 founded with each other, would form the mastoido-humeralis of the Dog, minus the 

 posterior portion, or the trachelo-acromialis, which is not represented in Man. 

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