CHAPTER IX 



THE* NERVOUS SYSTEM 



Animal and Vegetative Functions Sensation, Motion, and Volition 

 The Structure of the Nervous System The White and Gray Sub- 

 stances The Brain Its Convolutions The Cerebellum The 

 Spinal Cord and its System of Nerves The Anterior and Posterior 

 Hoots The Sympathetic System of Nerves The Properties of Ner- 

 vous Tissue* Excitability of Nervous Tissues The Functions of the 

 Spinal Nerves and Cord The Direction of the Fibres of the Cord 

 Reflex Activity, and its Uses The Functions of the Medulla Oblon- 

 gata and the Cranial Ganglia The Eeflex Action of the Brain 

 Effects of Alcohol, Tobacco, Snuff, Narcotics, Opium, Chloral, Hash- 

 eesh, Chloroform 



1. Animal Functions. The vital processes which we have 

 been considering in the three previous chapters of digestion, 

 circulation, and respiration belong to the class of functions 

 known as vegetative functions. That is, they are common to 

 vegetables as well as animals ; for the plant, like the animal, 

 can originate nothing, not even the smallest particle of matter ; 

 and yet it grows, blossoms, and bears fruit, by reason of obtain- 

 ing and digesting the nutriment which the air and soil provide. 

 The plant has its circulatory fluid and channels, by which the 

 nutriment is distributed to all its parts. It has, also, a curious 

 apparatus in its foliage, by which it abstracts from the air 

 those gaseous elements so necessary to its support ; and thus it 

 accomplishes vegetable respiration. These vegetative functions 

 have their beginning and end within the organism of the plant ; 

 and their object is the preservation of the plant itself, as well 

 as of the entire species. 



1. What processes are known as the vegetative functions? Why so called? What 

 properties and functions does the plant possess ? Their object T 



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