ANIMAL ANOMALIES 659 



Polydactylism (Extra Digits) 



There are numerous abnormal variations in the number and ar- 

 rangement of digits, ranging from a stumplike structure of no digits 

 through the ''lobster claw" condition of two or three, to as many 

 as two more than normal. The polydactylous condition is rather 

 frequently found in cats. In fact, Wilder once reported that pos- 

 sibly 25 per cent of the cats of the vicinity of Ithaca, N. Y., possessed 

 an extra digit on each foot. The forefeet shown in Fig. 357 are 

 from a living cat which came from a litter of four, two of which 

 showed these complete characteristics on all feet, one of the litter 

 had only an extra toe on one foot, and the fourth was normal. Both 

 hind feet of this animal had five well-developed digits instead of the 

 usual four. This condition is a hereditary one and is brought about 

 by partial duplication of elementary structures. 





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Fig. 357. — Front feet of a half -grown kitten with six toes. The claws are pro- 

 tracted on the left foot and retracted on the right There were five toes on the 

 hind feet of this cat. 



Conjoined Twins 



Instances occur in which individuals of about equal size or of 

 unequal size are fused together. If this occurs at the hips with 

 dorsal sides together, the condition is usually known as Siamese 

 twins. There are a number of different varieties of fusion, includ- 

 ing the head region, chest region, or complete fusion of trunk into 

 a single body with two heads and vice versa. A chicken with two 

 pairs of legs and wings, two backs, and a single head has been 

 dissected and described by Dr. F. L. Fitzpatrick. The feather tracts 

 were double on the neck and trunk. Internal dissection showed 

 the single digestive system to extend between the two necks, follow 

 through the combined body cavity with some modifications, and 

 empty into the cloaca of the right back region. No cloaca was pres- 



