THE STRUCTURE OF MAN 



of the body. The elbow and knee joints are turned slightly 

 outwards, the convexity of the former facing slightly backwards, 

 that of the latter slightly forwards. The supporting portion of 

 the limb looks in both cases outwards, and in each the anterior 

 digit is rightly considered as the first of the series. 



FIG. 65. LARVAL SALAMANDEB. (After Hatschek.) 

 A, with the limbs turned down ; B, with the limbs turned up. 



In the higher Quadrupeds the anterior and posterior limbs 

 undergo characteristic changes of position. First, the supporting 

 segments of the two limbs (i.e. the manus and pes) are rotated 

 inwards, so that their long axes, which were originally transverse 

 to that of the body, come to be parallel with it [and their 

 originally anterior borders become internal] ; as a natural result of 

 this, the first digit (pollex or hallux) becomes the innermost and 

 the fifth the outermost. The rest of the limb, however, differs in 

 its behaviour in the two members. In the fore-limb the humeral 

 and radio-ulnar segments become flexed in such a way that the 

 elbow is no longer directed outwards but backwards (cf. Fig. 65). 

 In the hind -limb, on the contrary, the basal (femoral and 

 tibio-fibular) segments are turned inwards, and so flexed that 

 the knee is directed forwards. According to Hatschek the 

 differences in position of the fore- and hind-limbs involve only 

 their basal segments, their terminal segments (manus and pes) 

 being displaced identically. It would follow from this that the 

 changed position of the fore-limb has little if anything to do with 

 the torsion of the humerus, which is very marked even in the 

 Salamander, and must therefore be referred back to an early 

 process antecedent to the changes under discussion. 



