726 



SOLIPEDA. 



and from the transverse processes of some of 

 the superior cervical vertebrae, passes down- 

 wards in front of the head of the humerus and 

 descends along the inner surface of the fore- 

 arm, into which it is ultimately inserted. 



The muscle of the shoulder which is proper 

 to quadrupeds may be named the trachelo- 

 acromialis (acromio-trachelien, Cuv., acromio- 

 basilaire, Vicq d'Azyr). It arises in the horse 

 from the transverse process of the atlas and 

 of the four following cervical vertebrae (in the 

 generality of quadrupeds from the three upper- 

 most only) ; from this origin it descends 

 towards the shoulder-joint, making its ap- 

 pearance externally between the two divi- 

 sions of the trapezius, which it separates ; it 

 then spreads out over the acromial portion 

 of the scapula, and descends as far as the 

 middle of the humerus, where it is inserted. 

 Its action will, of course, be to draw the 

 shoulder upwards and forwards. This muscle, 

 which exists in all the mammalia, with the 

 exception of the human species, would seem 

 to be in special relation with the quadrupedal 

 mode of progression ; and, as Cuvier observes, 

 affords a striking example of the difficulty of 

 establishing a good nomenclature in com- 

 parative anatomy : in some animals, it derives 

 its origin exclusively from the cranium ; and, 

 in others, from the upper or lower cervical 

 vertebrae. Its mode of insertion is equally 

 various ; in the tapir it is implanted into the 

 aponeurosis which covers the deltoid muscle ; 

 while, in the horse, it has its insertion into 

 the middle portion of the humerus by two 

 aponeurotic tendons, which embrace the bra- 

 chialis internus muscle. 



The serratus major anticus (scapulo-costieri), 

 in the horse, arises from the transverse pro- 

 cesses of the third, fourth, fifth, and sixth 

 cervical vertebrae, and also from the external 

 surfaces of the six superior ribs : its origins 

 extending as far backwards as the insertion of 

 the tendons of the sacro-lumbalis : from this 

 extensive origin it passes backwards around 

 the chest to be implanted into the base of the 

 scapula, its insertion occupying nearly half of 

 the internal surface of that bone. This muscle, 

 Cuvier remarks, is much more extensively 

 developed in quadrupeds than in the human 

 subject ; for, in all other mammalia, except in 

 the orang-outang, it arises not only by digi- 

 tations from the ribs, but also from the trans- 

 verse processes of the vertebrae of the neck, 

 an arrangement which becomes necessary in 

 animals that walk upon four feet, in order to 

 prevent the scapula from being pushed too 

 far backwards towards the spine. This muscle, 

 in fact, forms, with its fellow on the opposite 

 side, a kind of sling, by which the trunk is 

 suspended. The fact that it is equally exten- 

 sive in its attachments in the Monkeys, is an 

 additional proof that the usual mode of pro- 

 gression in these animals is on four feet : in 

 these an'mals, indeed, the serratus magnus 

 derives origins from all the cervical vertebrae, 

 instead of from only a part, as in other mam- 

 mifera. In the Cetaceae that do not walk, 

 and in the kangaroos which have their ante- 



rior limbs very small, the serratus magnus 

 presents a corresponding feebleness of deve- 

 lopment. 



The pectoralis minor (serratus minor anticus) 

 is, in the horse, represented by a muscle, 

 which, arising from the sternum and from the 

 first, second, third, and fourth ribs near their 

 sternal terminations, runs upwards and back- 

 wards to be inserted into the superior costa 

 of the scapula near the base of that bone ; it 

 also contracts tendinous attachments with 

 the aponeurotic covering of the teres minor 

 and other scapular muscles. 



The rhomboideus arises, in the horse, entirely 

 from the ligamentum nuchae, and from the 

 spines of the anterior dorsal vertebrae, whence 

 it runs outwards to be affixed to the base of 

 the scapula. 



In monkeys and in the carnivorous qua- 

 drupeds the rhomboideus is continued up- 

 wards as far as the occiput, whence it derives 

 an extensive origin; the occipital portion, 

 indeed, is, in the Carnivora, separated from 

 the rest so as to form a distinct muscle, called 

 by some writers the occipito-scajmtaris, and, 

 by Cuvier, " rhombo'ide de la tete." 



The omo-hyoideus is, generally, wanting in 

 animals whose scapula presents no coracoid 

 process : neither can there be any subdavius 

 in animals that do not possess a clavicle : in 

 the horse, however, the former of these is 

 represented by a strong muscular fasciculus. 



In this place it may be proper to notice the 

 muscle named by the human anatomist sterno- 

 cleido-mastoideus ; but which, in the lower ani- 

 mals, is represented by two distinct muscles. 

 One of these, 



The sterno-mastoideus, or, as it might be 

 named, sterno-maxillaris, arises, in the horse, 

 from the anterior end of the sternum, and, 

 running forwards strong and fleshy, is inserted 

 by a flat tendon into the inferior maxilla under- 

 neath the parotid gland, sending, however, 

 another tendon to be implanted into the root 

 of the mastoid process. 



The cleido-mastoideus, always a distinct 

 muscle from the preceding, is, as we have seen 

 above, in the horse and other non-claviculate 

 quadrupeds, confounded with the clavicular 

 portions of the trape2ius and deltoid. 



Muscles inserted into the humerus. The 

 movements of the humerus in the human 

 body are effected by two sets of muscles : one 

 derived from the trunk, the other from the 

 framework of the shoulder. The former are 

 the pectoralis major and latissimus dorsi ; the 

 latter, the supra-spinatus, the infra-spinatus, 

 and the subscapularis proceeding from the 

 surfaces of the scapula and the deltoid, teres 

 minor, teres major, and coraco-brachialis, which 

 take their origins from the processes. In the 

 horse and in other quadrupeds, various cir- 

 cumstances render modifications in the ar- 

 rangement of these muscles indispensable. 



The pectoralis major (sterno-humerien), in 

 the horse, arises, first, from the aponeurosis 

 of the external oblique muscle of the ab- 

 domen ; secondly, from the two lower thirds 

 of the sternum ; and, thirdly, from the supe- 



