GENERAL STRUCTURE. 31 



of the cells of the body, but merely that portion of the 

 food not transformed into a condition permitting it to be 

 absorbed by the villi. 



In addition to these systems necessary for the main- 

 tenance of life, the cat requires a means for supporting 

 the body and moving about, furnished by the osseous 

 and muscular systems. The osseous system serves not 

 only for support and locomotion, but also for the pro- 

 tection of the delicate vital organs. The skull and spinal 

 column contain the brain and spinal cord, while the 

 heart and lungs are well shielded by the dorsal vertebrae, 

 the ribs, and sternum. Likewise the muscles ward off 

 serious injuries from the blood-vessels, as they cover to 

 a considerable depth nearly all large arteries, and also 

 aid by their contraction in moving the lymph through 

 the numerous lymphatic vessels extending from the 

 extremities to the jugular veins. 



These systems previously described are capable of per- 

 forming their functions only when supplied with nerves 

 through which impulses can be transmitted from the 

 brain and spinal cord. Stimuli sent by the brain or cord 

 through the nerves cause the gastric juice to flow into 

 the stomach, the bile and pancreatic secretions to be 

 formed and poured forth into the intestines, the kidneys 

 to eliminate the waste from the blood, the heart to beat, 

 and the muscles to contract and relax. 



The only system which is not absolutely necessary to 

 the life of the cat is the reproductive; but this is required 

 for the continuance of the species. It is not, however, 

 functional during the entire life, but as a rule only from 

 the end of the first to the tenth year. 



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