1867.] 265 [Wynian. 



connection with the vertebral coUimn through the scapular and pelvic 

 arches is only secondary, as is that of the teeth with the jaws. 



HUMERUS AND FEMUR. 



Fig. 9. Fig. 10. 



Fig. 9. Femur of an alligator. Fig. 10. Humerus of an alligator. 



All agree that these two are homotypes, the only question is whether 

 they are to be compared ;is parallel or as symmetrical bones; this an- 

 swered, the parts which correspond are easily determined. As has al- 

 ready been stated, the majority of anatomists describe them as parallel 

 repetitions. One of the difficulties which is encountered in this mode, 

 is the fai;t that the knees and elbows in all animals are bent so as to 

 form angles pointing in opposite directions. To meet this, Vicq 

 d'Azyr, in comparing the limbs, turned the elbow forwards, but in do- 

 ing so the head of the humerus was found to face in one direction, and 

 that of the femur in the opposite one. He then compared the limbs 

 of opposite sides ; in this case, not only was the limb placed in an un- 

 natural oosition, but although the heads of the bones faced in the same 

 direction, the thumb was on one side of the hand, and the great 

 toe on :he other side of tlie foot. He simply exchanged asymmetry 

 of the heads of the humerus and femur for ' asymmetry of hands and 

 feet, and so the difficulty was not obviated. Maclise, in his article 

 "Skeletcn," in the Cyclopaedia of Anatomy and Physiology, and Martins 

 in his INIemoir, meet this difficulty by supposing the humerus twisted 

 through 180°. " In primitive construction both members are identical, 

 but this secondary modification, viz., the torsion of the humerus, is 

 that circamstance which distinguishes them one from the other. While 

 in idea I untwist the humerus, by bringing its back to the front, I 

 at the same time unravel the gordian knot of that problem which has 

 so long existed as a mystery for the homologist." * According to 

 Martins, " the femur is straight and has no torsion. The humerus be- 

 ing a twisted femur, if we wish to compare the two, it is fii-st of all 



* Cyclop. Anat. and Physiol. Article Skeleton, p. 666. 



