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CHAPTER XVII. 



NERVOUS ACTION. 



Muscular irritability and nervous stimuli. Reflex actions. Physical 

 nervous actions. Mental nervous actions. Nerve-cells and fibres. 

 Their functions. Analysis of nervous matter. Spinal cord. Its 

 structure and functions. Functions of the groups of cells. Crossing 

 of sensitive impressions on the cord. The brain. Oblong medulla. 

 Pons varolii. Cerebrum. Cerebellum. Their functions. Uses of the 

 medulla in respiration and deglutition. Vital point. Effects of prick- 

 ing the floor of the fourth ventricle. Effect of removing the cere- 

 bellum. Turning or rolling as a result of injury to certain parts. 

 Removal of the cerebrum in birds, and its effects. Cranial nerves. 

 Olfactory nerves. Optic nerves. Their functions. The influence of 

 their crucial and other fibres. Auditory nerves. Common motor nerves 

 of the eye. Pathetic nerve. Abducent nerves. Trifacial nerves. 

 Their varied functions. Sympathetic ganglia on their course. Facial 

 nerve. Its influence on the salivary glands. Glosso-pharyngeal nerves 

 Their influence on deglutition. Pneumogastric nerves. Chauveau's 

 experiments. Effects on breathing. Effects on the lungs when di- 

 vided. Action on the heart ; on the stomach. Spinal accessory 

 nerves ; their influence on the voice. Hypoglossal nerves. 



THE nervous system is that part of the animal body to 

 which all others are subservient, since it possesses the 

 power of controlling and harmonizing the various functions 

 essential to life. 



The organs and tissues of the economy are, by virtue of 

 properties inherent to them, capable of responding to stimuli 

 or exciting causes, in such a manner as leads to the exercise 

 of their individual functions. This inherent property is 



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