THE SKELETON. 61 
n the camel, deer, sheep, and cow two. In the last three 
‘orms the metacarpals present are the third and fourth, 
vhich in the adult are coalesced into a single bone known 
S the cannon-bone. Remnants of the second and fifth 
netacarpals are present in the deer, sheep, and cow, as the 
mall caudo-lateral hoofs indicate. The functional meta- 
arpal present in the horse is the third. The reduction of 
netacarpals in the ancestral forms of the horse is shown in 
igure 35, and will be referred to again in the description of 
he phalanges. 
Phalanges.—The cat has five toes or digits on the fore- 
oot, called poller, index, medius, annulus, and minimus. 
tach digit, except the pollex, consists of three phalanges 
Fig. 36). The pollex or thumb has only two phalanges. 
[he row of phalanges articulating with the metacarpals 
s called the proximal, the terminal row the distal, and 
he remaining row the middle phalanges. Two small 
esamoid bones are attached on the volar side of the junc- 
ion of each proximal phalanx with the metacarpal. Each 
listal phalanx has its proximal end produced caudal on the 
ialmar aspect so that its articular surface faces dorsal. The 
listal phalanges terminate in claws which are retractile. 
The number of digits in the forefoot of Mammalia varies 
rom one to five. Nearly all the species of every order ex- 
ept the Edentata and Ungulata possess five digits. The 
apir has four functional digits. The cow, deer, sheep, and 
ig also have four digits, but only two are functional, the 
econd and the fifth being atrophied and terminating in the 
mall caudo-lateral hoofs which do not touch the ground. 
“he rhinoceros has three functional digits, and the Equide 
ossess only one digit (Fig. 37), the third, though the 
trophied remnants of the second and fourth metacarpals 
re present as splint bones which do not support phalanges. 
As before stated, the Ungulates are undoubtedly de- 
