THE MUSCULAR SYSTEM 



221 



cases this correspondence is at least suggested in certain details 

 of the muscular system. Here, in Necturus, however, the 

 correspondence of the free limbs from elbow or knee down is 

 practically an exact one, and includes, not only the skeletal 

 parts, but the muscles, arteries and nerves, precisely what 

 would be expected in this primitive form if the serial homology 

 is really fundamental and not due to secondary modification 

 through a similarity of use. 



Proximal to the elbow and knee, however, there is little if 

 any correspondence or even similarity in the musculature, cor- 

 responding in this respect to the great differences in the two 

 girdles, and therefore for descriptive purposes the limb may be 

 divided into unlike proximal portions, to be treated separately, 



FIG. 58. Lateral view of shoulder muscles of Necturus. 



Id, latissimus dorsi; ds, dorso-scapularis; t, trapezius; /, omohyoid; k, levator 

 anguli scapulae; la, levatores arcuum; d, dorso-trachealis; ph, procoraco-humeralis; as, 

 anconeus scapularis; al, anconeus lateralis. 



and similar distal portions, which are almost identical and may 

 thus be considered together. The first will include the girdle 

 and the proximal joint of the free limb, the upper arm or thigh, 

 and the second the remainder, or that from elbow or knee to 

 the end. 



The principal muscles of the proximal portion of the anterior 

 limb in Necturus are shown in figures 52 and 58. Of these 

 certain are extrinsic and extend from trunk or head to the 

 appendicular skeleton ; others are intrinsic, both origin and in- 

 sertion being upon the latter part. 



Conspicuous among the first is the latissimus dorsi, certain 

 parts of which are still seen to arise from myocommata in the 

 form of elements in the act of separating themselves from the 



