VARIATION. 73 



articular surfaces and general form of the bone, although 

 it has been unfortunately lost. 



304. The skeleton of the right manus of a Horse, with an additional 



largely developed digit intercalated between the inner 

 splint-bone and middle toe. The second row of carpal 

 bones is fortunately preserved, and exhibits an additional 

 bone, probably an os magnum. A great deal of irregularly 

 ossified tissue surrounds both digits. The horse was shod 

 on both toes. Presented by Lawson Tait, Esq. } 1872. 



305. The skeleton of the right manus and pes of a half-grown 



Cat. The manus possesses seven digits ; there are also 

 two trapezoid bones in the carpus, and the proximal ex- 

 tremity of the metacarpal bone of an eighth digit is 

 apparent. The pes has five digits. 



In the manus the digits are arranged in the following order, 

 beginning from the inner side of the hand : A preternaturally 

 slender thumb and a second digit (index), having its ungual and 

 median phalanges like those of a left digit, are articulated with 

 the trapezium and inner trapezoid respectively ; a second thumb, 

 consisting of three phalanges, is attached to the outer side of the 

 index by ligament: a second index with normal right charac- 

 ters follows; its metacarpal bone does not reach the second 

 trapezoid but ends in a point above and is joined by ankylosis 

 to the head of a third metacarpal bone so intimately that it appears 

 at first sight to be a portion of that bone ; no other portion of an 

 accessory third digit exists ; the remaining digits are the normal 

 third, fourth, and fifth. It appears as if the inner side of this 

 manus has been doubled, the accessory toes being reversed and 

 afterwards fused in obliquely behind and inside the normal digits. 

 In the pes the second digit is supplemented by an additional 

 reversed second digit. The middle cuneiform is also double. The 

 inner cuneiform exists, but the normal rudiment of a hallux is 

 absent. 



Presented by B. T. Lowne, Esq. 



306. The left manus and pes of the same animal, exhibiting the 



same malformation, dissected to show the muscles. 

 In the manus a distinct extensor muscle, proprius pollicis, goes 

 to the accessory or inner thumb, and a second similar muscle goes 

 to the phalanges of the accessory index. It has probably been de- 

 tached from its proper thumb, which is extremely minute and has 

 become united with the finger which bears it. There is a flexor 

 brevis pollicis (?) to the same finger. 



