THOKACIC LIMBS 



649 



FIG. 51lA. 



Radius. 

 Scapho-lunar. 



Trapezoid, 



Ulna. 



Cuneiform. 



Unciform. 



Magnum. 



(b) Middle phalanx, the insertion of the palmaris longus and 

 the flexor sublimis digitorum, the extensor communis 

 digitorum, and the extensor minimi digiti. 



(<?) Distal phalanx, the insertion of the flexor profundus 

 digitorum. 



VARIATIONS IN THE HAND. 



An important abnormality of the hand is produced by an increase 

 in the number of the fingers. This condition, which is known as 

 polydactylism, is not uncommon in -the 

 cat, and instances have been reported in 

 which it has run through families for 

 several generations. 1 



The additional fingers are always 

 added to the radial, or thumb, side of 

 the hand, and the index, middle, ring, 

 and little fingers always remain normal. 

 The additional fingers may be perfectly 

 developed, or be in part rudimentary ; 

 they may be free or joined together. 

 The terminal phalanx of an additional 

 finger either may be retracted into an 

 excavation on the radial side of the 

 middle phalanx, when the digit is said 

 " to be formed like a digit of the opposite hand," or, inasmuch as the 

 middle phalanx is not excavated on either side, cannot be retracted at 

 all ; in this case the digit is termed " indifferent." 



Both hands are usually simultaneously abnormal, in the same 

 manner but not necessarily to the same extent ; when the hands are 

 abnormal the feet also may be abnormal. 



According to Bateson, 2 the known examples of polydactylism in 

 the hand of the cat may be grouped in three classes : 



1. The hand has five digits, the normal number, but the thumb 

 has three phalanges and is formed like a digit of the opposite hand. 



2. The hand has six digits, all with three phalanges. The first 

 digit is indifferent, the second is formed like a digit of the opposite 



1 Poulton, Nature, 1883, p. 20 ; 1887, p. 38. 



2 Materials for the Study of Variation, pp. 313-324. 



LEFT HAND WITH SUPERNUMERARY 

 DIGITS. 



