68 



HUMAN BIOLOGY 



acquired a set of muscles which served to raise, lower, bend 

 or warp the paddles or. to move them forward or backward. 

 When some of these fish scrambled out on land the muscles 



Fig. 7. Musculature of fore paddle of existing lobe-finned fish Polypterus. 



(After Klaatsch, Die Brustflosse der Crossopterygier.) 



of the paddles became further strengthened and differ- 

 entiated, so that soon they were able to support the weight 

 of the body (Gregory, 1915). 



These primitive hmbs were at first short, thick, held far 

 out from the body and sharply bent at the elbows and 

 knees. The serratus muscles on either side of the neck sent 

 strips to the inner surfaces of the shoulder girdle and thus 

 the fore part of the body was slung between the u-shaped 

 shoulder girdle, which had been inherited from the fishes. 



At this stage the pelvis had no direct connection with the 

 backbone. In front view it was v-shaped, with the opposite 

 femora spreading out on either side from the lower part of 



