THE MUSCLES OP THE LIMBS. 49 



An omohyoid muscle frequently connects the scapula with 

 the hyoidean arch. 



The posterior limb does not seem to offer any miTscles 

 exactly homologous with the foregoing. So far, however, 

 as the recti abdominis, the obliqims externus, and the fibres 

 of the erector spince, are attached to the j)elvic girdle, they 

 coiTespond in a general way with the pre-axial, or protractor, 

 muscles of the pectoral arch; and the ischio-coccygeal 

 muscles, when they are developed, are, in relation to the 

 pelvic arch, retractors, though, owing to the relative fixity 

 of the pelvis, they act in protracting, or flexing, the caudal 

 region. 



The psoas minor, proceeding from the under- surfaces of 

 posterior dorsal (or lumbar) vertebrae to the ilium, or pubis, 

 is a protractor of the pelvis, but, as a hyposkeletal muscle, 

 has no homologue in the fore limb. 



Extrinsic muscles attached to the hmnerus or femur, on the 

 dorsal aspect. — In the fore limb there is the post-axial latissi- 

 mus dorsi passing from spines of dorsal vertebrse to the 

 humerus. On the ventral aspect, the pectoralis major extends 

 from the sternum and ribs to the humeinis. 



In the hind limb, the glutceus maximus, so far as it arises 

 from the sacral and coccygeal vertebrae, and is inserted into 

 the femur, repeats the relations of the latissimus dorsi. In 

 the absence of anything corresponding with the steimum, or 

 the ribs, no exact homologue of the pectoralis major can be 

 said to exist, though the pectineus comes near it. The psoas 

 major, passing from posterior dorsal or liimbar vertebras — the 

 pyriformis from sacral vertebrae — ^q femoro-coccy<jeiis (when 

 it exists) from caudal vertebrae — to the femur, are all hypo- 

 skeletal muscles, without homologues in the anterior ex- 

 tremity. 



All the other muscles of the limbs are intrinsic, taking 

 their origins from the pectoral or pelvic arches, or from 

 some of the more proximal segments of the limb- skeleton, 

 and having their insertion in the more distal segments. 

 They are thus aiTanged in Man and the higher Mammalia .- 

 - Intrinsic muscles proceeding from the pectoral or pelvic 



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