INTRODUCTOKY 7 



the origin of the spinal nerves from the spinal cord in series ; the 

 arrangement of muscles ; and the resemblance between the anterior 

 and the posterior limbs. 



The body of a vertebrate may be said to be made up of two lon- 

 gitudinal tubes. 



O 



On the dorsal side of the body, in the skull and spinal column, 

 is a long tube, the neural canal, for the brain and spinal cord ; on 

 the ventral side is a larger tube surrounded partly by bone, partly by 

 muscles, and known as the body cavity. This ventral cavity contains 

 the alimentary canal and its appendages, the lungs, the heart and great 

 blood-vessels, and the central organs of the uro-genital system. It is 

 divided transversely by a muscular partition into two parts, whereof 

 the cavity near the head is the thoracic cavity, containing the thoracic 

 viscera, chiefly the heart and lungs, and the cavity near the tail is 

 the abdominal cavity, containing the abdominal viscera, which com- 

 prise most of the alimentary and uro-genital systems. 



THE SKELETON. 



The skeleton in a comprehensive sense consists of the bones, 

 the cartilages, with the ligaments that bind them together, and all 

 that fibrous framework which surrounds and penetrates the organs 



FIG. 3. 



THE SKELETON OF THE CAT. 



