A CASE OF A SYNDACTYLOUS CAT il 



various types of malformation which occur in the extremities. 

 Bateson ('94, p. 399) finds the cases of Polydactyly more regular 

 than those of syndactyly. Polydactyly, in its simplest form, 

 may consist in the reduplication of a single phalanx. The 

 intermediate step between it and the normal condition is the 

 development of a third phalanx on the first digit or thumb. The 

 reduplication may proceed so far as to include the metacarpal 

 and metatarsal bones of several digits of hands and feet. Syn- 

 dactyly seems to be more irregular in its manifestations. Cutane- 

 ous and fibrous forms occur in which only the fleshy parts of the 

 extremities are affected. It may result from the omission of 

 certain skeletal elements or from fusion of some of the bones. 

 In such cases there is a corresponding syndactyly of the fleshy 

 parts. The omission may occur in either marginal or central 

 digits. The latter is less common and is called split hand or 

 split foot (Broman, '04, pp. 651, 230-231). According to Lewis 

 ('09, p. 7), split foot may be accompanied by polydactylous 

 hands and split foot is never found unaccompanied by split foot. 

 Defects in the wrist bones may occur. A single carpal or tarsal 

 bone may completely fail or may fuse with a neighboring bone. 

 In the case of an omission of one of the carpal or tarsal bones, 

 there is usually a coincident defect of the bones either distal or 

 proximal. (Broman, '04, p. 651). 



In either Polydactyly or syndactyly the abnormal condition 

 is apt to be symmetrical (Broman, '04, p. 231) and to be more 

 pronounced distally than proximally. This distal syndactyly was 

 particularly conspicuous in the cat under discussion. Bateson 

 finds this difficult to understand. He says ('94, p. 357), 



The rule that in the lowest condition of syndactylism of the bones 

 it is conimonh' at the periphery that the union is most complete is 

 also difficult to understand in connexion with the fact that the division 

 of digits in the lowest forms of polydactylism appears also in the pe- 

 ripheral phalanges. 



Syndactyly and Polydactyly, then, are both heritable and are 

 frequently found in association. Each consists in an abnormal 

 number of skeletal parts, the one in less and the other in greater 

 number. The abnormality is usually more pronounced at the 



