GESEIIAL CHAKACTEfiS OF THE VEUTEBIiATA. 



223 



2. The bone wliicli forms the upper portion of the Hmb proper, and 

 which is known as the humerus {h). 3. Two bones which form the 

 mi(h.lle portion of the hmb {e.g., the foi-e-arm in man), ami which are 

 known as the radius and tdna (r and m), of which tlie formei- is 

 the bone mainly concerned in carryhig the hand or fore-foot. 4. A 

 number of small bones, which form the wrist, and are termed the 

 carpus (d). 5. The cylindrical bones (usually five in numlier) which 

 form the root of the hand, and are known as 

 the metacarpus (in). 6. The bones which form 

 the fingers proper, and wliich are known as 

 the phcdanges (p). 



Essentially the same parts can lie traced in 

 the hind-limb of a typical Vertebrate animal, 

 but they are known by diffeient names. The 

 bones wliich unite the limlj to the trunk are 

 usually more or less completely united to- 

 gether, constituting a single mass, known as 

 the iiviominate hone (fig. 161, i). This is fol- 

 lowed by a long cylindrical bone, which 

 forms the upper portion of the hind-limli, 

 and is known as the "thigh-bone," or fimu/r 

 (f). Following this are the two bones of 

 the shank, corresponding to the radius and 

 ulna of the fore-limb, and known as the tibia 

 and fibula (t and ,s'). fjf these, the tdjia {t) 

 corresponds to the radiu.t, and is mainly con- 

 cei'ned in cariying the foot. Next conies a 

 series of small bones, which form the ankle, 

 and are known as the tarsus (r). This is 

 succeeded by a series of cylindiical lioiies 

 (usually five in number), which form the 

 root of the foot, and which are termed the 

 metatarsus (m). Finally, the metatarsus is 

 succeeded by the bones of the toes, which in 

 this case are again termed the jj/talavges (p). 

 In both limbs the usual numlier of phalanges 

 to each toe or " digit " is three. 



The digestive system of the VerttRirata does not recpiire a length- 

 ened notice. The mouth is usually furnished with inih, whicli 

 have for their chief function the reduction of the food to a cuuditinn 

 in which it can be digested. In some animals, linwe\-er, such as the 

 snakes, the teeth are only used to hold the ijrey, and not for masti- 

 cation ; and in others, such as the turtles and liirds, the jaws are not 

 fiirnished with any teeth at all. ' The food is also usually subjected 



