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anatomy will give us the most accurate information upon the subject of 

 these serial homologies. The theories of position which we have to ex- 

 amine in the first place are five, first — that of Professor Owen ("Nature of 

 Limbs," 1849), that the front of the arm represents the front of the thigh, 

 the biceps cubiti representing the rectus femoris ; but this is open to 

 the objection, that it homologates joints which have reverse actions, and 

 is contrary to the disposition of the bony and muscular parts of the 

 limb, although based upon some striking peculiarities in the limbs of Mar- 

 supials as the upward prolongation of the fibula in the Wombat, which is 

 interpreted as a patella by Owen ; secondly, the theory of Maclise (Art. 

 Skeleton, Todd's " Cyclopaedia," vol. iv., p. 852), that the lower end of 

 the humerus has been twisted round, as indicated by the musculo-spiral 

 groove, and hence the displacement of the parts of the limb below. This 

 has been strongly defended by Martens (Nouvelle comparaison des mem- 

 bres pelviens et thoraciques ("Memoiresde l'Academie des Sciences et 

 Lettres, Montpellier," torn, iii., p. 4, 1857) ; but to it there are many ob- 

 jections, that the bony fibres show no sign of such a twist ; that we have 

 no embryonic evidence of torsion; that the muscles present us with no 

 appearances in favour of such a change ;* thirdly, we have the theory 

 Vicq D'Azyr, that the left arm and the right leg correspond, an idea 

 which we will revert to afterwards, and which is severely reviewed 

 by Martens (loo. cit. p. 474) ; fourthly, we have the theory proposed by 

 Mr. Huxley, in the Hunterian Lectures for 1864, that the bony points 

 at the upper end of the primal limb bone resemble their alternates, that 

 is, the greater trochanter femoris corresponds to the lesser tuberosity 

 of the humerus, and vice versa, and that the supraspinatus is the 

 homotype of the iliacus. These views he bases upon the structure of 

 Ornithorhynchus, and the arrangement of the trochanters of Choice- 

 pus, Galeopithecus and Pteropus, and it is defended by Mr. Mivart 

 in his very valuable monograph on the myology of Echidna hystrix 

 (" Trans. Linn. Soc," vol. xxv., p. 396, et seq.); bat although bearing 

 with it the weight of great names, and very striking peculiarities of 

 structure in these aberrant forms of Mammalia, I would venture to 

 dissent from this very original and striking theory, and that upon the 

 following grounds : first, it seems contrary to the anatomical structures 

 of the great majority of animals, in which the correspondence between 

 the greater trochanter and greater tuberosity is more than a mere 

 fancied resemblance; secondly, because in three of the Chelonians 

 which I have examined (selected because in them the basal bone of the 

 two extremities so nearly correspond), the hawksbill turtle, Emys 

 geographica, and Testudo grceca, the correspondences of arrangement, 

 both in the bones and muscles of the two limbs, were not what might 

 be expected in conformity with the theory — the greater trochanteric 



* It is particularly when it comes to deal with the soft parts that the fallacy of this 

 theory appears, and the consideration that it requires the brachialis anticus to act as the 

 representative of the crurasus is enough to stamp it as not accordant with anatomical fact. 



