200 ELEMENTS OE OBNITHOLOGT. 



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 X for tendons. It may be more or less cartilaginous or 

 a separate ossicle. 



"When there is a hallux it is supported by n small separate 

 metatarsal of its own, which is applied to the back of the lower 

 part of the much longer tq,rso-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 for the 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 If the occasional existence of " spurs." 



* See ante, ^. 193. 



t This is coiaparable with the " cannon-bone " of an ox, which is not 

 essentially a single bone, but consists of two metatarsals anohylosed together. 

 I See below, p. 206. § See ante, p. 193. 



I See a7ite, p. 159. f See ante, p. 164. 



