200 ELEMENTS OF ORNITHOLOGY. 
it. We saw * that the metacarpus of Birds answers to three of 
the bones of the fleshy part of our hand, each of which three 
bones is in us called a “ metacarpal.” In the same way the 
tarso-metatarsal bone of Birds answers to three (only in the 
Ostrich to no more than two) of the bones of the fleshy part of 
our foot, each of which three bones is in us called a metatarsal. 
Evidence of this complexity is afforded at the distal end of the 
bone t, which exhibits three convex articular surfaces for articu- 
lation with the bones of the second, third, and fourth toes (or 
digits) respectively. This essential complexity is clearly shown 
in the extremely short tarso-metatarsal bone of the Penguin, 
by large apertures left between its middle and its inner and 
outer metatarsal elements. Similar but much smaller apertures 
are to be detected in other birds. The three metatarsals do not 
lie in the same plane, the median one inclining more backwardly 
at its proximal end, and more forwards at its distal termination, 
than do the other two metatarsals. 
At the upper end of the tarso-metatarsal bone there is gene- 
rally a backwardly projecting calcaneal process—or hypotarsus,— 
which may be marked by vertical grooves or perforated by small 
canals t for tendons. It may be more or less cartilaginous or 
a separate ossicle. 
When there is a hallux it is supported by a small separate 
metatarsal of its own, which is applied to the back of the lower 
part of the much longer tarso-metatarsal bone. This meta- 
tarsal, which answers to that of our great toe, ends freely 
above in a styliform process. Below it develops an articular 
surface forthe proximal bone of the first digit of the foot—the 
hallux. 
Very rarely the first metatarsal is long, and still more rarely 
it anchyloses with the tarso-metatarsal bone. 
The bones of the toes, or digits of the foot, are——like those of 
the digits of the pinion §—called phalanges. Their number has 
been already indicated || when we pointed out the number of 
joints in the toes, with which number that of the phalanges 
corresponds. 
We have already noted 4 the occasional existence of ‘ spurs.” 
* See ante, p. 192. 
+ This is comparable with the ‘cannon-bone” of an ox, which is not 
essentially a single bone, but consists of two metatarsals anchylosed together. 
t See below, p. 206, § See ante, p. 193. 
|| See ante, p. 159. {| See ante, p. 164. 
