18G9.] 79 [Coues. 



passu, it would seem, with the rate of increase of the normal number 

 of segments. Instances of duplication of a whole limb are so ex- 

 tremely rare that they bear, perhaps, no computable proportion to 

 those in which distal segments alone are abnormally multiplied, ap- 

 pearing in the form of supernumerary digits ; and I have not before 

 met with, nor do I recollect seeing any record of, a case wherein the 

 modification by redundancy was so profound as to affect the scapular 

 or pelvic arch. On the other hand, extra digits are so common, as 

 well in lower animals as in our own species, that statistical tables 

 have been drawn up, showing the percentage of their occurrence, 

 their comparative frequency upon one or both sides of the body, and 

 upon the fore and hind limbs, as well as, to a degree, the influence of 

 race, sex, temperament, etc., in their production ; and even permitting 

 some application to them of the law of antero-posterior, as well as 

 bilateral, symmetry. 1 



This chick's malformation by redundancy appears utterly refrac- 

 tory, violating the first principles usually found to hold in cases of 

 monstrosity by duplication of parts, and carrying the heteromorphy 

 to the greatest possible degree; inasmuch as the two supernumerary 

 legs are both on the same side, both composed of the normal number 

 of osseous segments, and both separately and movably articulated 

 with the pelvic arch ; the latter presenting three acetabula on one 

 side, and being otherwise modified in shape. But even in the obscu- 

 rity of this extreme modification, no less of a hsemal arch than of its 

 diverging appendages, may be discerned a curious and instructive 

 display of the force of the law of bilateral symmetry, operating under 

 well-nigh hopeless circumstances. 



At Columbia, S. C, early in April, 1868, my attention was invited 

 to a "four-legged chicken" that had just been hatched, forming one 

 of a numerous brood, all the rest of which were perfect. The little 

 creature appeared healthy, and was well-formed, except that it had 

 three legs on the left side. It ate freely, and the only trouble it had 

 was in walking ; for although seemingly so well provided for in the 

 matter of legs, it could only use one of the four to any advantage, 

 the others being useless encumbrances. In moving it hopped on the 

 right leg, occasionally supporting itself on the foremost left one, while 



1 Consult, in this connection, Prof. B. G. Wilder's able and instructive paper, 

 "Extra Digits," in the Publications of the Massachusetts Medical Society, Vol. 

 II, No. 3. 



