Wyman.] 266 [June 5, 



necessary to untwist it (detordre Vhumerus) the effect of which is to 

 place the epitrochlea (inner condyle) outwards, and the epicondyle 

 (outer condyle) Inwards. This done, the comparison of the pelvic and 

 thoracic extremities offers no further difficulty."* That this does not 

 quite clear up the matter even to M. Martins, appears a little further 

 on, where he admits what he calls a " metaphysical difficulty " {diffi- 

 cidle metaphi/siqiie), viz., that the humerus never was literally twisted; 

 "it is a virtual toi"sion, which Avas never mechanically effected"; "but 

 this virtual torsion has produced all the consequences of a real one."f 

 In another place he infornis us that "L'humerus n'est point un os 

 d'abord droit, qui se torde ensuite. II y a mieux l'humerus est tordu 

 avant d'exister." ! In order to put the bone in the untwisted condition he 

 supposes it plastic, as when the lime has been removed by acid, or, to 

 make a mechanical illustration practicable, he cuts the bone in two, 

 puts a peg in the medullary cavity and rotates the lower half 180°. 

 Any one, however, who will take an arm from an articulated skeleton, 

 place the palm on the table, and then following his directions in im- 

 agination, or by the mechanical process, and rotates the humerus 180° 

 from within outwards, (the direction necessary to untwist it) he will 

 find a real, and not a metaphysical difficulty. In the ordinary prone 

 position of the hand, the radius is already partly wound around the 

 ulna, and will completely encircle it when the hu-.nerus is "untwisted," 

 thus producing a much greater distortion than the one attempted to be 

 obviated. Mr. Humphrey has already pointed out other difficulties in 

 the way of this view of Martins, and we will only add that the lines 

 supposed to indicate torsion simply grow out of the mode of attach- 

 ment of the muscles to the bone, and in no way indicate a twisting of 

 it. The bone primarily was smooth, and the ridges were built up on 

 it as the muscles themselves were developed, without the ends of the 

 bones having in any way changed their relative position. 



If the two bones are supposed to be symmetrical repetitions, no diffi- 

 culties arise. They will have the position which is natural to them in 

 the animal series; the axis of the humerus will incline backwards, and 

 that of the femur forwards. The articidating convex surfaces of the 

 lower end of the humerus will face forwards, while those of the femur 

 will face backwards. The back of the humerus, which is on the side 

 of the extensor muscles of the fore arm, will be opposed to that part 

 of the thigh which is on the side of the extensor muscles of the leg. 



* Memoir, p. 482. t Idem, p. 490. 



