208 VERTEBRATE ZOOLOGY 



The Neck. The neck is short and strong. In land mammals 

 the length of the neck is usually correlated with the length of the 

 forelegs ; an animal with long legs has a long neck. This is be- 

 cause the mouth is the usual organ of prehension, and the animals 

 seize their food on or near the ground. The length of the neck and 

 head must be such that the mouth is brought to the ground when 

 the head is bent down. 



The neck in all land vertebrates is a flexible body division, its 

 principal function being to give the head a wide range of move- 

 ment ; this is important, inasmuch as the head bears, besides the 

 organs of prehension, the special sense organs, which are the prin- 

 cipal organs of orientation. 



The Trunk. This region is made up of the thoracic, lumbar, and 

 sacral subregions. The first and third of these are rigid regions and 

 support the two pairs of extremities ; the second is a flexible one. 



The thoracic subregion is the animal's chest; it contains the 

 heart and lungs, which are inclosed in a bony case composed of 

 the spinal column, the ribs, and the breastbone. It contains also 

 the pectoral girdle, by means of which the skeleton of the fore 

 limbs is joined with the trunk. This girdle consists principally of 

 the two large shoulder blades, or scapulae, which are embedded in 

 the muscles of the back and sides. Two pairs of nipples are present 

 on the ventral side of this region. 



The lumbar subregion is the animal's abdomen ; it contains the 

 bulk of the important viscera. Its walls are strengthened dor- 

 sally by the spinal column, the transverse processes of which are 

 here very long; laterally and ventrally they have no bony sup- 

 port. This subregion forms the pivot of the body ; it is the place 

 where the body bends when the direction of movement is changed. 

 It follows, consequently, that an active and agile animal like the 

 cat has a relatively large lumbar region. In a two-legged verte- 

 brate, like the bird, the body does not bend when the direction of 

 movement is changed, and the lumbar region is not functional 

 in this way. Three pairs of nipples are present on the ventral side 

 of this region in the cat. 



The sacral subregion is the most rigid portion of the body ex- 

 cept the head. In it lie the hinder portions of the digestive and 



