60 
Fic. 37. Laterat As- 
PEcT OF Lerr  Fore- 
LIMB OF EQuus. 
Humerus; ts, third 
h, 
ELEMENTS OF MAMMALIAN ANATOMY. 
The typical arrangement of the vertebrate carpus is 
shown in figure 36, B. The pisiform does not belong to the 
metacarpal; mu, fourth 
metacarpal; p, phalan- 
ges; r, radius; s, sesa- 
moid; sc, scapula; ua, 
ulna; a, scaphoid; c, 
semilunar; m, cunei- 
form; a, pisiform; zw, 
magnum; w, unciform. 
cartilaginous skeleton, but is a sesa- 
In all mammals pos- 
sessing five digits, the anlage of 
three bones in the proximal row, 
five bones in the distal row, and a 
central element occurs in the embryo, 
but through fusion of elements a 
less number is present in most adults. 
Thus, in the cat the radiale and in- 
termedium and centrale unite to form 
the scapholunar. In all forms car- 
palia 4 and 5 coalesce to form the 
unciform. 
Metacarpus.— There are five 
metacarpal bones forming the middle 
region of the forefoot. They are 
named, beginning on the pollex side, 
first, second, third, fourth, and fifth 
metacar pals respectively. Each bone 
consists of a proximal extremity or 
base, a middle portion or shaft, and 
a distal extremity or head (Fig. 
360). 
to be slightly convex on the dorsal 
aspect. 
The number of metacarpals in 
mammals varies from one in Equus 
to five which are present in most 
orders. Nearly all the species of every 
order, except the Edentata and Un- 
moid bone. 
These bones are curved so as 
gulata, possess five metacarpals. In the pig and hippopota- 
mus there are four metacarpals, in the rhinoceros three, and 
