SOLIPEDA. 



723 



half the breadth of the muscle from the 

 superior edge of all the ribs, except two or 

 three of the most anterior ; and its slips are in- 

 se ted by as many distinct tendons into the 

 interior edge of all the ribs, except two or 

 three of the hindmost, and also into the trans- 

 verse process of the seventh vertebra of the 

 neck. The continuation of this muscle, the 

 cervicalis descendcns, offers nothing remarkable. 



The multifidus spince, in the dorsal region 

 arises by numerous tendinous origins from 

 the transverse processes of the vertebrae of 

 the back, loins, and sacrum, near their pos- 

 terior protuberances, each slip running for- 

 wards to be inserted into the spinous pro- 

 cess of the vertebra in front of that from 

 which it derives its origin, the whole forming 

 a thick mass, which fills up the hollow situated 

 between the spinous and transverse processes. 

 In the neck a similar disposition exists. 



The intertransversarii colli take their origins 

 from the roots of the oblique processes of 

 the cervical vertebrae, and from between these 

 and the transverse processes : in the horse 

 they are of great strength and importance, 

 running forwards to be inserted into the trans- 

 verse processes of the vertebra in front of that 

 from which they arise. In addition to the above 

 there is a set of muscles named by Stubbs the 

 intervertebrales, which do not exist in the hu- 

 man subject : these arise from the ascending 

 oblique processes of the five inferior vertebra? 

 of the neck, and from the space betwixt the 

 oblique processes of the uppermost vertebrae 

 of the back : they are each of them inserted 

 into the lateral parts of the bodies of the ver- 

 tebrae above their origin. 



The longus colli is the only muscle, ex- 

 clusively appropriated to the movements of 

 the spine, situated in front of the spinal 

 column. This muscle, in the horse, arises 

 from the transverse processes of the third, 

 fourth, fifth, and sixth vertebras of the neck, 

 from which origins it runs upwards to be in- 

 serted by distinct tendons into the anterior 

 part of the bodies and transverse processes 

 of the vertebrae above them, and into the 

 anterior surface of the atlas. 



The quadratics lumborum offers the same 

 disposition as in the human subject. 



The tail in quadrupeds, from its great de- 

 velopment, requires for its movements a special 

 set of muscles, of which scarcely any traces 

 exist in the human subject. This organ in 

 the horse is susceptible of three kinds of 

 movements. It can be straightened or ele- 

 vated, bent or brought downwards, and lastly 

 carried to either side. These movements, 

 again, by their combinations, produce secon- 

 dary effects, so that the tail becomes suscep- 

 tible of very extensive motions ; and, in such 

 quadrupeds as have this part very largely de- 

 veloped, it even supplies the place of a hand, 

 so completely is it under muscular control. 



In order to effect these different movements, 

 three* distinct sets of muscles are employed, 

 which are arranged upon the same plan as the 



* Cuvier, Anat. Comp. torn. i. p 275. 



long muscles in other parts of the spinal 

 column ; that is to say, they arise by numerous 

 tendinous slips, and are inserted in a similar 

 manner, the slips of origin and insertion run- 

 ning, of course, in opposite directions : the 

 latter, moreover, are prolonged to a much 

 greater extent than in the rest of the spinal 

 column, and firmly bound down to the ver- 

 tebrae by tendinous sheaths, so as to add as 

 little as possible to the bulk of the tail. 



The muscles which raise or straighten the 

 tail are all situated upon its upper aspect : they 

 are, first, 



The sacro-coccygcus superior (lombo-sus- 

 caudien'). This muscle arises in the horse 

 from the inferior or posterior edge of the third 

 spinal process of the os sacrum, and from the 

 spines, edges, and interspinal ligaments of the 

 sacral vertebra? behind that point, as well 

 as from those caudal vertebra that are pos- 

 sessed of spinous apophyses. The fleshy 

 mass formed from these origins gives off 

 numerous slender tendons : the first of these 

 is the shortest, and runs inwards to be in- 

 serted into the base of the first caudal ver- 

 tebra, in which the articular apophyses are 

 wanting. The second tendon is inserted in a 

 similar manner into the succeeding vertebral 

 piece; the third into the next, and so on to the 

 end of the tail. The number of the tendons 

 given off' is, of course, determined by that of 

 the vertebrae. Each tendon is lodged in a sort 

 of ligamentous canal, which forms a sheath 

 for it throughout its whole course. When 

 these two muscles act in concert the tail is 

 necessarily raised upwards. 



The interspinales superiores (spinalis ob- 

 lifjiius ; lombu-sacro-coccygienofVicq d'Azyr). 

 These muscles are a continuation of the inter- 

 spinous muscles of the spine; but as the 

 spinous processes of the tail are short, and 

 frequently replaced by two tubercles answer- 

 ing to rudiments of the oblique processes, these 

 muscles are here disposed obliquely, being 

 more widely separated posteriorly than they 

 are in front. 



The muscles which depress the tail or bend 

 it downwards all take their origin in the in- 

 terior of the pelvis, and are prolonged to a 

 greater or less extent along the inferior aspect 

 of the tail. These form, when completely 

 developed, four pairs, or four pairs of series, 

 of muscles. 



1. The ilco-cocci/gei (ifeo-sous- caudi< n of 

 Vicq d'Azyr) arise from the internal or pelvic 

 surface of the ossa ilei, and, forming an elong- 

 ated fleshy belly in the interior of the pelvis, 

 terminate beneath the root of the tail, which 

 they will consequently depress with consider- 

 able force against the anus. 



2. The sacro-coccygeiis inferior (sacro-sous- 

 cujidien) is the antagonist of the sacro-coccy- 

 geus superior, above described, which in struc- 

 ture it exactly resembles. This muscle takes 

 its origin from the inferior surface of the 

 sacrum and of the transverse processes of 

 those caudal vertebrae in which these pro- 

 cesses are developed, by a fleshy belly which 

 gradually diminishes in thickness, and termi- 



3 A 2 



