354 



MANUAL OF ZOOLOGY. 



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

 two to three cylindrical bones, which are known as the 

 pJialanges {/). 



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 

 iliu7n, ischium, and /«to— which are usually 

 anchylosed together, and form conjointly what 

 is known as ^^ innominate bone (fig. 128, i). 

 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-hmb 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. Lasdy, the 

 metatarsus carries the digits, which consist of 

 from two to three small bones or phalanges, as 

 Fi^. 128. — Pelvic in the fore-limb. 

 or''ci'impani?e) ^hc digestive system of Vertebrates will be 

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

 /F=Z,"orthi^h: brief sketch may be given here of the general 

 Fb'i' ' ^t'^'^' * phenomena of digestion. All Vertebrate ani- 

 wMetktarsus; > mals are provided with a mouth for the re- 

 Phaianges of the geption of food, and in the great majority of 

 cases the mouth is furnished with teeth, which 

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

 monly to cut and bruise the food, arid thus render it capable 

 of digestion. The food- is also generally subjected in the 

 mouth to the action of " salivary " glands, the secretion of 

 which serves not only to moisten the food, and thus me- 

 chanically 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, 



