90 LAND MAMMALS IN THE WESTERN HEMISPHERE 



the jumping rodents called jerboas, have it only in the pes. 

 The first (or inner) metatarsal, that of the great toe, or hallux, 

 is sometimes opposable to the others, as in the monkeys, apes 

 and lemurs. 



The word metapodial is a useful general term which in- 

 cludes both metacarpals and metatarsals. A metapodial 

 with its phalanges is a digit, a term often employed because 

 of the ambiguity which arises in the use of the words "fingers" 

 and "toes," and is applicable to both fore and hind feet. 



Normally, the phalanges of the pes are so like those of the 

 manus as to require no particular description ; and only when 

 the two pairs of extremities are specialized for entirely different 

 functions, is there any notable divergence between the pha- 

 langes of manus and pes. 



Before leaving the subject of the skeleton, it will be well 

 to explain the terms used in describing the gait and manner of 

 using the feet. When the entire sole of the foot is in contact 

 with the ground and weight is thrown upon the heel-bone, or 



calcaneum, the gait is said to 

 be plantigrade and is exem- 

 plified in Man, bears, raccoons 

 and many other mammals. 

 The Dog is digitigrade, that is 

 to say, the feet in the stand- 

 FiG. 42.-Left pes of Black Bear (t7r.u. i^g positiou are nearly erect 



amenca«u.s), showing the plantigrade gait, and the Wrist and heel are 

 T., tibia. F., fibia. Cal., calcaneum. • i i • i i i i 



^s., astragalus. A^., navicular. Cn.3, raiSCd high aboVC the grOUlld ; 



external cuneiform. Cb., cuboid. Mt.V, the Weight is bome UpOU ball- 

 fifth metatarsal. 



like pads, one under the pha- 

 langes of each functional digit and one under the metapo- 

 dials. The digitigrade gait is found not only in all the dogs 

 and cats, but in many other Carnivora and in the camels and 

 llamas, as well. Transitions between the plantigrade and 

 digitigrade gait are so numerous and gradual, that such terms as 

 semi-plantigrade and semi-digitigrade are sometimes necessary. 



