'i-2-2 



VERTEBRATE ANIMALS. 



Ill the typical vertebra the segment is completed by a second 

 arch, which is jilaced in front of or beneath the body of the verte- 

 bra, and which is known as the " htemal ' ai-oh, as it includes and 

 protects the principal organs of the blood -circulation (fig. 158, B). 

 This second arch is often only recognisable with great difficulty, as 

 its parts are generally much modified ; but 

 a good example may be obtained in the 

 human thorax. Here, attached to the front 

 of the vertebrse, we find a series of bony 

 arches, known as the ribs (r), followed by a 

 series of cartilaginous pieces of a similar 

 shape, termed the "costal cartilages" (p), the 

 whole united in front by a central bone, 

 known as the bi'eastbone or " sternum " (b). 

 As a general rule, amongst the higher 

 Vertebrates, the following regions may be 

 recognised in the vertebral column : Firstly, 

 the cervical region (fig. 159, c), comprising a 

 variable number of vertebrre, which con- 

 stitute the neck, and immediately follow 

 the head. Secondly, the cervical region is 

 succeeded by a variable number of vertebrie 

 which usually carry ribs, and are known as 

 the dorsal vertebree {d), or vertebrae of the 

 back. Thirdly come certain vertebrae which 

 constitute the lumbar region (l), or the 

 region of the loins. Fourthly, there usually 

 follows a series of vertebrie which are im- 

 movably united together to form a single 

 bone, which is termed the sacrum (s). 

 Lastly, there comes a variable series of 

 vertebrie which are usually free and mov- 

 able upon one another, and which con- 

 stitute the caudal region, or the region of 

 the tail (0- 



The nature of the bones which enter into 

 the composition of the limbs varies somewhat 

 ill different Vertebrates in accordance with 

 their mode of life ; but in all the higher 

 members of the sub-kingdom the limbs ai-e built upon a general and 

 easily recognisable type. The fore-limb consists generally of the 

 following parts : 1. A series of bones uniting the limb to the trunk, 

 the two most important being the shoulder-blade (scajnila, fig. 160, «) 

 and the corncnid, while a collar-bone (rhiviclr) may also be present. 



fig. 100.— Fore -limb of the 

 Chimpanzee, c Collar-bone, 

 or clavicle ; s Shonlder- 

 Ijlaile, or .scapula ; h Bone 

 of the upl'i-r arm, or liunier 

 us; r Railius ; u Ulna; d 

 Bones of the wrist, or car- 

 pus ; m B(^iifs nf tlie root 

 of the hand, oi- metacarpus ; 

 p Bones of the digits, 

 phalanges. 



