16 



THE GAT. 



[CHAP. ii. 



is traversed by large blood-vessels and by the alimentary tube, which 

 extends continuously from the mouth backwards to its posterior 

 termination. The parts of which the cat's body are composed are 



Fig. 2. DIAGRAM REPRESENTING A VERTICAL SECTION- THROUGH THE CAT'S BODY. 



11. Brain and spinal marrow contained within 

 the skull and backbone, which are deep 

 black. 



st. Breast-bone. 



dd. Alimentary canal. 



s. Stomach. 



h. Heart. 



cc. Great blood-vessels. 



11. Urinary bladder. 



sy. Chain of sympathetic ganglia. 



ill. Diaphragm. 



thus conveniently divisible into the bones, with their membranes 

 the skeleton ; the muscles ; the nervous system and organs of sense ; 

 the system of vessels, or circulatory system ; the alimentary tube, 

 with its appendages ; the lungs and kidneys, with certain other 

 parts, and the organs of reproduction. 



THE SKELETON. 



2. The word " skeleton " is popularly taken to denote only the 

 bones, with the cartilage or gristle which may be connected with 

 them. It should, however, be taken to mean not only these but 

 also the membranes, which radiating from the bones and cartilages 

 invest every organ of the body, and finally clothe it externally in 

 the form of " skin." Such membranes penetrate the very bones 

 themselves and support the marrow they contain ; they separate 

 every muscle from its neighbour, and surround and line each tube 

 and passage in the body ; so that if every other tissue could be dis- 

 solved away and yet this fibrous tissue be left, we should have 

 a complete outline model, as it were, of the cat's entire frame. 



3. This substance, which is, as it were, the basis of the skeleton, 

 is formed of what is called CONNECTIVE TISSUE, which consists of a 

 mass of delicate white fibres imbedded in a structureless material or 

 " ground substance ; " scattered through this are minute particles of 

 protoplasm, called " corpuscles," which are more or less rounded or 



