2G6 COMPARATIVE MYOLOGY. 



times reacliing the eighth rib, and the longus colli is separuhle into a riglit and 

 left portion. 



The remarks made regarding the costil, dorso-lnmbar, and abdominal 

 muscles of the hog are, for the most part, applicable here. In the pectoral 

 region also there is little to call for remark, unless it be that the transversus 

 and parvus are very small and thin. The following features presented by the 

 muscles of the sub-lumbar region should be noted. The quadratus lumborum 

 attains its maximum of relative size in the dog, and with it is blended the 

 psoas jJarviis y the jisoas magnus, smaller and shorter than the parvus, becomes 

 so blended posteriorly with the iliacus that they may almost be regarded as 

 one muscle. Neither of the psoe muscles project into the thoracic cavity. 



Pectoral Limb. 



The scapular and brachial muscles are large, corresponding to the develop- 

 ment of the bones. Placed before the teres externus is a distinct acromio- 

 humeralis muscle. The antea and j^ostea spina'.i have each only one tendon of 

 insertion, that of the former going to the external humeral trochanter. The 

 coraco-humcralis and flexor brachii resemble those of the hog, the former being 

 short, and inserted just above the insertion of the teres internus. 



The antibrachial region includes some muscles, the consideration of which is 

 of importance. The tendon of the extensor metacarpi magmis divides, and is 

 attached to the heads of the first and second — i.e., the two inner metacarpal 

 bones — while the extensor obliquus is inserted to the metacarpal element of the 

 pollex or thumb. The extensor communis digitorum has a tendon divided into 

 four parts, a part going to each distal phalanx, while the extensor inopriiis 

 tendon is trifurcated and attached to the three outer distal phalanges. The 

 flexor perf or attis tendon divides into four, that of the perforans into five parts, 

 the first being attached to the median phalanges of the four principal digits, 

 the other to the distal phalanges of all the digits. The ulnaris and radialis 

 accessorii are present. The extensor pollicis et indicis arises with the extensor 

 metacarpi obliquus on the outer aspect of the radius ; its tendon accompanies 

 that of the extensor communis through its sheath, bifurcates, and is inserted 

 to the pollex and first digit. 



The following muscles occur in the antibrachial region, and are the intrinsic 

 rotators. The supinator longus, a very delicate band, arises internally along 

 with the extensor metacarpi magnus, and is inserted to the inner distal 

 extremity of the radius ; in the dog its action as a supinator is almost nil. 

 The supinator brevis is a short radiating miiscle, covering the elbow joint in 

 front ; it arises from the outer distal end of the humerus and lateral ligament, 

 and is inserted to the anterior and inner parts of the head of the radius. It 

 snpinates the extremity — i.e., it tends to turn the anterior aspect outwards. 

 The pronator teres is a short, thick muscle, arising from a small process on the 

 internal epicondyle, and becoming inserted to the inner border of the radial 

 shaft, at about a third from its head ; it rotates the extremity, opposing the 

 supinator. The p)ronator quadratus is deeply seated under the flexor group of 

 muscles ; it extends almost from the elbow joint to the carpus, and joins the 

 radius to the ulna, its fibres passing directly from one bone to the other ; it 

 acts as a pronator. 



There are fifteen muscles in the metacarpal region of the dog, all of which 



