The other muscles belonging to the atlas— namely, the rectus anticus, the rectus lateralis, and the obliquus superior — offer the same position as in the man.
The muscles derived from the axis—viz. the rectus posticus major and the obliguus in ferior — are likewise similarly disposed in all quadrupeds. • The muscles arising from the other cervical vertebrm are The complexus, which, commencing from the upper oblique process of the third ver tebra of the neck, continues its origin from all the oblique processes of the neck below that point, as well as from the upper oblique process of the first vertebra of the back, also by a pretty strong tendon from the transverse processes of the second and third dorsal ver tebrm ; from these origins it runs forwards to be inserted by a strong round tendon into the occiput close to its fellow of the opposite side : in this course it is connected by numer ous tendinous processes with the ligamentum nuchx. That portion of the complexus usu ally distinguished by the name of digastricris colli is in the horse undistinguishable as a distinct muscle.
The trachelo-mastoidens, or complexus minor, arises from the oblique processes of the third, fourth, fifth, sixth, and seventh cervical and first dorsal vertebrm, and froin the transverse processes of the second and third vertebrm of the back ; it runs forwards external to the last-mentioned muscles to be inserted by a strong tendon into the mastoid apophysis of the temporal bone. The above muscles are overlapped by the Splenius capitis (cervico-nzastoiden), which, arising by strong tendinous processes from the spinous processes of the two superior dorsal and two last cervical, and also exten sively from the ligamentum nuchze, runs for vvard to be inserted into the transverse pro cesses of the fifth, fourth, and third cervical vertebra, and into the transverse ridge of the occipital bone. It is remarked by Cuvier that in carnivorous quadrupeds the splenius is not inserted into the transverse processes of the cervical vertebrae as it is in herbivorous animals and in the human subject, in which the latter portion is sometimes sufficiently distinct to obtain the name of splenius colli in contra distinction to the splenizts capitis. It is like
wise remarkable that in the camel, if the splenius exists at all, it is extremely thin and difficult to display by dissection.
Muscles of the ribs and sternum.— The mus cles derived flom and inserted into the ribs and sternum found in all quadrupeds to have the same general arrangement as in the human subject. In the horse, their disposi tion is as follows, beginning with those whose office is to raise the framework of the chest and thus assist in inspiration.
The scaleni differ in no remarkable respect from the corresponding muscles in the human body. The same may be said of the inter costal muscles, the levatores costarum, the ser ratus posticus superior (dorso-costien), the ser rains posticus inferior (lonzbo-costien), and the triangularis sterni (sterno-costien), the two latter of which must be regarded as depressors of the ribs, and consequently acting the part of muscles of expiration.
In all quadrupeds possessing a greater num ber of ribs, aud consequently a more capacious thorax than man, the attachments of the dia phragm are found to be much further re moved from the margins of the false ribs than in the human subject : nevertheless the position which it occupies, and its connections in the thoracic cavity, are similar in all mainmiferous animals.
The walls of the abdonzen, in the horse as in the generality of quadrupeds, are composed of five pairs of muscles, to which the same names are applicable as are bestowed upon them by the anthropotomist.
The obliquus externus abdonzinis dominien) arises, by tendinous processes that indigitate with the origins of the serratus rnagnus, from the external surface of all the lower ribs, beginning at the fifth ; and below the last rib it derives its posterior attach ment from the fascia lumborum ; fiom these origins, it runs backwards and downwards, terminating in a broad tendinous expansion, the terminations of which in the linea alba, os pubis, and Poupart's ligament, together with the formation of the external abdominal ring, are exactly as in the human subject.