SOLIPEDA. 



727 



rior part of the sternum for about one-third 

 of its length. The first of these portions 

 winds round to be inserted; into the internal 

 aspect of the head of the hiimerus ; the second 

 ends in a fascia, which descends downwards 

 over the fore-arm, while the third, running in 

 a transverse direction over the inferior portion, 

 is inserted into the humerus along with the 

 " levator humeri proprius "between the biceps 

 and the brachiaeus internus. 



In all those mammalia which are destitute 

 of complete clavicles, even in the Cetacea, 

 there is a part of the sternal portion of the 

 pectoralis major, which is inserted perpen- 

 dicularly into the humerus, that joins the cor- 

 responding portion of the opposite side to 

 form the muscle common to both arms," by the 

 action of which the two fore-legs are made to 

 cross each other. 



The latissimus dorsi (lombo-humerieri), in 

 the horse, and in other quadrupeds, exhibits 

 the same arrangement as in the human sub- 

 ject : it is, however, in the lower animals 

 powerfully assisted in its action by the massy 

 muscle already described (cutano-humerienj, 

 formed by the panniculus carnosus, a strong 

 tendon from which is inserted into the hume- 

 rus along with that of the latissimus dorsi. 

 Both are intimately connected with the tendon 

 of the teres major, and from this combination 

 of tendons arises one of the heads of the 

 triceps extensor cubiti. 



The supra-spinatus, the infra-spinatus, the 

 subscapularis, the teres major, and the teres 

 minor have, in all quadrupeds, the same ar- 

 rangement as in the human subject, the only 

 differences, being dependent upon the shape 

 and proportions of the scapula. 



The deltoid in all animals having their 

 clavicles imperfect or wanting, is neces- 

 sarily modified in its disposition to a very 

 considerable degree. We have already seen 

 when speaking of the trapezius, that its cla- 

 vicular portion is in such cases blended with 

 the anterior division of that muscle : that part 

 only which takes its origin from the scapula 

 remains to be noticed. Where the acromion 

 is well developed, the deltoid may be divided 

 into two portions ; one derived from the aero-* 

 mion, the other proceeding from the spine 

 and subjacent surface of the scapula : these 

 two portions unite, and, decussating each other, 

 form a common tendon, which is implanted 

 into the deltoid ridge of the humerus. As 

 the acromion process diminishes in size, the 

 acromial portion of the deltoid becomes en- 

 feebled in like degree, until at length, as in the 

 horse, where there is no acromial projection, 

 that part of the deltoid arising from the spine 

 remains alone. Under these circumstances, 

 this muscle is directed forwards in nearly the 

 same direction as the infra-spinatus, and, both 

 from its position and office has been named 

 by hippotomists the " abductor longus brachii." 



The coraco-brachialis exists even in animals 

 that have no coracoid process, in which case 

 it takes its origin from a little tubercle situ- 

 ated upon the superior costa of the scapula. 

 When the biceps arises by two heads, as in 



the human subject, the coraco-brachialis arises 

 with the longer head by a common tendon ; 

 but when, as is the case in many quadrupeds, 

 the biceps has but one origin from the humerus, 

 the coraco-brachialis is in no way connected 

 with that muscle.. 



Muscles of the forearm. Flexors. The bi- 

 ceps, in the generality of quadrupeds, has the 

 same origins as in the human subject ; one 

 head arising from the neck of the scapula, 

 the other from its eoracoid process : these 

 two heads uniting form a common tendon, 

 which is inserted into the tubercle of the 

 radius, and, by an aponeurotic expansion into 

 the fascia covering the muscles of the fore- 

 arm ; but where the coracoid process of the 

 scapula is deficient, as in the horse, and in the 

 carnivora generally, the term " biceps " is no 

 longer applicable to this muscle, seeing that 

 it has but one origin from the margin of the 

 glenoid cavity : in the rest of its course it is 

 similarly disposed in all the mammalia. 



The brachicBiis internus (Jiumero-cubitien} in 

 all quadrupeds has the same arrangement as 

 in the human subject. In the horse, the biceps 

 and the brachiaeus are by most writers named 

 the " long and short flexors of the forearm." 



Extensors. The triceps extensor cubiti 

 {scapulo-olecranicn) is in the horse a muscle 

 of prodigious strength, and consists of three 

 portions similar to those named in the human 

 anatomy the long extensor, the short exten- 

 sor, and the brachialis externus (the great 

 extensor,, the middle extensor, and the short 

 extensor of Bourgelat, and other writers on 

 the anatomy of the horse). There is, more- 

 over, a fourth portion, derived from the com- 

 mon tendon of the latissimus dorsi and teres 

 major, by the intervention of which, it takes 

 its origin from the inferior margin of the sca- 

 pula. 



The anconcem (epicondylo cubitien} exists in 

 all quadrupeds. 



As might be expected from the construction 

 of the bones of the forearm, both the pronator 

 muscles are in the Solipeda entirely wanting, 

 as is the case in the Ruminantia and in the 

 Pachydermata generally ; nevertheless, in the 

 elephant and in the hog-tribe the pronator 

 teres is feebly developed ; and, as the mobility 

 of the bones of the forearm becomes more 

 perfect, as in the Carnivora, Quadrumanaand 

 Marsupialia, both the pronators are found pre- 

 senting the same arrangement as in the human 

 body. 



The supinators are quite obliterated in the 

 Solipeda, as well as in the Ruminantia and 

 Pachydermata. 



Muscles of the carpus and metacarpus, 

 The muscles employed in bending the wrist 

 are in our own persons the palmaris longus, 

 the flexor carpi radialis longior, the flexor 

 carpi radialis brevior, the extensor carpi ra- 

 dialis, the flexor carpi ulnaris, and the ex- 

 tensor carpi ulnaris ; of these one only is in- 

 serted into the carpus, all the rest being 

 attached to the metacarpal bones. 



In all multi-digitate mammalia, such as the 

 Quadrumana, Carnivora, Rodentia, and Eden- 



3 A 4 



