332 



MANUAL OF ZOOLOGY. 



which also vary in number, but are composed each of from 



two to three cylindrical bones, which are known as the 



phalanges (p\ 



Homologous parts are, as a rule, readily recognisable in the 



hind-limb. The pelvic arch, by which the hind-limb is united 

 with the trunk, consists of three pieces the 

 ilium, ischium, and pubes which are usually 

 anchylosed together, and form conjointly what 

 is known as the innominate bone (fig. 120, /). 

 In most Mammals, the two innominate bones 

 unite in front by a ligamentous or cartilaginous 

 union and they constitute, with the sacrum, what 

 is known as the pelvis. The hind -limb proper 

 consists of the following parts : i. The thigh- 

 bone or femur, corresponding with the humerus 

 in the fore-limb. 2. The bones of the shank, 

 corresponding with the radius and ulna of the 

 fore-limb, and known as the tibia and fibula. 

 Of these, the tibia is mainly or altogether con- 

 cerned in carrying the foot, and it is thus 

 shown to correspond to the radius, whilst the 

 fibula corresponds to the ulna. ' 3. The small 

 bones of the ankle, known as the tarsus, and 

 varying in number in different cases. 4. A 

 variable number of cylindrical bones (normally 

 five), which are called the metatarsus, and which 

 correspond to the metacarpus. 5. Lastly, the 

 metatarsus carries the digits, which consist of 

 from two to three small bones or phalanges, as 



Fig. 120. Pelvic in the fore-limb. 



of mb SpaJSee The di g est e system of Vertebrates will be 



(after Owen), i spoken of at greater length hereafter; but a 



/F$! brief sketch ma y be g iven here of the g eneral 



bone; t Tibia; s phenomena of digestion. All Vertebrate ani- 



Fibula; r Tarsus; , . , , . , , r , 



m Metatarsus; p mals are provided with a mouth for the re- 

 Sj! anges f the ce P tion of food, and in the great majority of 

 cases the mouth is furnished with teeth, which 

 are used sometimes merely to hold to the prey, but more 

 commonly to cut and bruise the food, and thus render it 

 capable of digestion. The food is also generally subjected 

 in the mouth to the action of " salivary " glands, the se- 

 cretion of which serves not only to moisten the food, and 

 thus mechanically assist deglutition, but also to render soluble 

 the starchy elements of the food. The food is next swallowed, 

 or, in other words, is transferred from the mouth to the stomach, 



