GENEEAL CIIAIiACTERS OF THE VEllTEBEATA. 



2-23 



f- 



2. The bone which forms the upper portion of the limb proper, and 

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

 middle portion of the limb (e.g., the fore-arm in man), and which are 

 known as the radius and ulna {r and «), of which the former is 

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

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

 carpus (d). 6. The cylindrical bones (usually five in number) which 

 form the root of the hand, and are known as 

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

 the fingers proper, and which are known as 

 the phalanges (p). 



Essentially the same parts can be traced in 

 the hind-limb of a typical Vertebrate animal, 

 but they are known by different names. The 

 bones which unite the limb to the trunk are 

 usually more or less completely united to- 

 gether, constituting a single mass, known as 

 the innominate bone (fig. 161,' i). This is fol- 

 lowed by a long cylindrical bone, which 

 forms the upper portion of the hind-limb, 

 and is known as the "thigh-bone," or femur 

 (/). Following this are the two bones of 

 the shank, corresponding tS the radius and 

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

 and fibula (t and s). Of these, the tibia [t) 

 corresponds to the radius, and is mainly con- 

 cerned in carrying the foot. Next comes a 

 series of small bones, which form the ankle, 

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

 succeeded by a series of cylindrical bones 

 (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 phalanges (p). 

 In both limbs the usual number of phalanges 

 to each toe or " digit " is three. 



The digestive system of the Vertebrata does not require a length- 

 ened notice. The mouth is usually furnished with teeth, which 

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

 in which it can be digested. In some animals, however, such as the 

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

 cation ; and in others, such as the tuitles and birds, the jaws are not 

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



Fig. 161.— Hind-limb of tlie 

 Cliimpaiizee. i Innomi- 

 nate bone: /Thigh-bone, 

 or femur ; ( Tibia ; s 

 Fibula : r Bones of the 

 ankle, or tar.sus ; m Meta- 

 tarsus ; p Phalanges. 



