40 HOUSE, GARDEN, AND FIELD 



short, and has only two phalanges ; the rest have three 

 each. The dog's hand is very like that of man, but the 

 thumb is short, and not opposable to the fingers. Notice 

 the strong claws and their firm insertion. 



Pig. There are four fingers, all bearing hoofs ; 3 and 

 4 are large, 2 and 5 much smaller, not reaching the ground ; 

 i (the thumb) is wanting altogether. 



Sheep or Ox. Two fingers (3, 4) bear hoofs ; there are 

 vestiges of fingers 2 and 5 in the form of small hoofs 

 without separate phalanges. The metacarpal (here called 

 the cannon-bone) is long and apparently single, but really 

 consists of the 3rd and 4th metacarpals united. In the 

 young sheep the bone has a double cavity. There are 

 splint-bones (vestiges of the 2nd and 5th metacarpals) on 

 the sides of the upper end of the cannon-bone. The long 

 fingers have each three sesamoid bones, that is, bony 

 nodules formed in tendons, usually opposite a joint. There 

 are two sesamoids behind the base of the first phalanx, 

 and one behind the base of the last phalanx. 



Horse. There is one finger only, the 3rd, with a meta- 

 carpal and three phalanges. Sesamoids as in the sheep. 

 The splint-bones, one on either side of the upper end of 

 the metacarpal, are the last vestiges of fingers 2 and 4. 



Bat. There are five fingers, of which the first (thumb) 

 is short and bears a claw ; the rest are prolonged, and 

 support the flying membrane. 



A common plan can be discovered in the fore limbs of 

 the man, dog, pig, sheep and horse. Even the wing of 

 a bird, though extremely unlike the rest, exhibits most of 

 the same parts ; we can distinguish quite easily the 

 humerus, radius, ulna, metacarpals and phalanges. No 

 hand has more than five fingers ; no hand has more than 

 two phalanges in the first finger (thumb). But though a 

 common plan may be traced in the hand of these different 

 animals, the plan is liable to be changed according to 

 special needs. The parts of the limb may be (i) enlarged, 

 (2) diminished, (3) suppressed, (4) fused together, (5) altered 



