OP THE NERVOUS SYSTEM. 463 



mal, and furnished with numerous centres and communicating 

 cords. Dr. Gall divides the nervous system of animal life into 

 those of the spinal marrow, the organs of sense, and those of the 

 brain and cerebellum. M. de Blainville considers the nervous 

 system as divided into as many parts as there are great func- 

 tions, and defines it to be masses or ganglia and filaments, some 

 issuing forth and going into the organ which they are to ani- 

 mate, which forms the particular life; others entering, and all 

 terminating in a central mass, establishing the general life, and 

 giving rise to the sympathies and relations. The central part, 

 according to this ingenious physiologist, is the spinal marrow; 

 another part comprises the ganglia of the organs of sense and 

 motion ; a third those of the viscera, viz. the cardiac and semi- 

 lunar or coeliac ganglions ; the fourth and last comprehends the 

 great sympathetic nerve, which forms a centre to the visceral 

 ganglia, and which, by the intervention of the ganglia of sen- 

 sation and motion, connects them with the central mass. 



All these divisions, which may be justified on various con- 

 siderations, are not, however, so well marked, so absolute as 

 their authors pretend. In man, the encephalon or some one 

 of its parts, the spinal marrow, where it is embraced by the 

 pons varolii, is certainly a centre to which the functions of all 

 the other parts of the nervous system are more or less subser- 

 vient. Indeed, in some of its functions, the spinal marrow 

 may be considered as a centre nearly independent; it is the 

 same with the ganglions, and finally, with the nerves; for no 

 part of the system is reduced to the entirely passive condition 

 of a conductor. This independence of the nerves, the greater 

 independence of the ganglions, and the still greater of the 

 spinal marrow, are otherwise so much the more distinctly 

 marked, as this or that function is concerned, as they are ob- 

 served in this or that animal, and as in man even they are ob- 

 served at more or less advanced periods of development. 

 These propositions, which may be regarded as the laws of 

 nervous action, will be developed hereafter. 



It is sufficient now to remark that there is no absolute sepa- 

 ration between the parts of the nervous system. We shall 

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