MYOLOGY. - The myology of quadrupeds is, in many points of' view, a subject of particular interest, more especially in those races which are far removed from man in their general habits or in the configuration of their skeleton. In the case of the Solipeds, owinr, to the exceedingly aberrant structure of their extremities, the disposition of their muscular system becomes a very important subject of inquiry, and it is partly from this cause, and partly from the necessity- of ob taining an accurate knowledge of the anatomy ofanimals so valuable to mankind, that the my ology of the horse and its congeners has been studied with great care, and delineated with extraordihary zeal and perseverance. It is for these reasons that we shall in the present article describe at some length this portion of their economy,..premising that the details here given will be found more or less applicable to quadrupeds generally, except where obvious peculiarities of structure belong to the class which forms the more immediate subject of our study.
Panniculus carnosus. — On removing the skin, the entire body is in most quadrupeds found to be invested with a muscular cover ing, the thickness and consequent importance of which varim in different parts. In the human subject the traces of this fleshy pan nide are very feeble, being confined to certain regions,— such as the anterior part of the neck, the palms of the hands, Sze. ; but in the horse it forms a much more important investment, giving mobility to the integument, and ma terially contributing to the support and de fence of various organs. This fleshy covering is very thick in the anterior region of the neck, whence it extends downwards upon the anterior extremities, and, becoming tendinous, is extensively inserted in conjunction with the tendons of the latissimus dorsi and teres major, into the external surfitce of the hu merus. From this point strong muscular fi bres pass downwards over the muscles of the fore-arm, where they terminate in a broad fascial expansion which embraces the lower part of the fore-leg. Another strong portion
of this fleshy tegument spreads over the sides and loins, where it degenerates into a tendino membranous layer, extending downwards as far as the penis, which it likewise invests with a carneo-membranous sheath. It likewise en cases the buttocks and thighs in a strong covering of fleshy and tendinous fibres, which spreads downwards over the fascia lata to the hind leg.
In describing the other parts of the mus cular system, it will be necessary to divide them into their appropriate regions, and in so doing, we shall follow the arrangement usually adopted in describing the human sub ject, beginning with the Proper muscles of the spine.— The long muscles of the spine, — viz. the spinalis and semi-spinalis dorsi, longissimus dorsi and sa cro-lumbalis—present a disposition very simi lar to what occurs in the human subject.
The spina& dorsi takes its origin from the spinous processes of the lumbar and posterior dorsal vertebrw, as well as frotn the broad fascia of the loins, and running forwards is in serted by distinct tendons into the spines of the anterior vertebrx of the back. Its con tinuation, the spinalis cervicis, is in the horse of great strength and importance: its origin commences from the second spine of the back, which origin is continued for about one third of the way down that spine towards its root : it arises likewise from the third dorsal spine and theligamentum nuchm ; from these origins it runs forward to be implanted by strong and distinct tendons into the spines of' the anterior cervical vertebrx.
The longissimus dorsi is situated immedi ately external to the spinalis, taking its origin from the common mass of muscle that arises beneath the lumbar fascia, as well as from the spinous processes of the loins and sacrum, whence it runs forward to be inserted by a double set of tendons into the transverse pro cesses of the loins and back, and also into the posterior ribs near their angles. Its continua tion, the transversalis is likewise of con siderable strength, but offers nothing worthy of remark.