550 DIVISIONS OF THE NERVOUS SYSTEM. 



expanded forward and upward so as to constitute a preponde- 

 rating mass of nervous substance, called encephalon or brain, 

 which retains all the instinctive properties found in similar 

 organs of the animals below him, and is endowed in addition 

 with the high and governing qualities of the mind ; some of 

 the organs, as those in the interior of his body, still living and 

 acting by a system of excito-motory or organic phenomena, 

 like those of the radiata, and for which we find arranged a 

 separate system of ganglia and nerves. 



— In tracing up the anatomy of the nervous system in this man- 

 ner, it will be found to consist entirely of the cineritious and 

 medullary neurine, variously disposed throughout the body, so 

 that the whole nervous structure, can be classed according to its 

 functions into three parts. 1st. Ganglia composed principally 

 of cineritious neurine, and which are believed to be the only 

 sources of power in the nervous system. 2d. Commissures or 

 bands which connect and associate the different ganglia with 

 each other, composed sometiiDes of the cineritious, but most 

 generally of the medullary neurine. And 3dly. Nerves or 

 cords, formed almost exclusively of the medullary neurine, 

 which establish communications between the ganglia, and all the 

 different portions of the body. The nerves are but the passive 

 agents of the ganglia, and have but a single and common func- 

 tion, and the commissures, so far as their offices have yet been 

 made out, have no more ; but the ganglia, differing among them- 

 selves greatly in size and form, seem on either half of the body 

 to be each one endowed with its peculiar function. Solly,* a 

 late writer on this subject, has fully carried out this idea in his 

 treatise on the brain. 



— Adopting at the outset, this rational and philosophical view 

 of the nervous system, the student will have a physiological 

 guide before him, which will, more satisfactorily than any 

 other, lead him through this interesting and important portion 

 of anatomy, that is yet far from being perfectly understood, 

 and is obscured by a multitude of terms, applied often coarsely 

 to different parts of the same physiological organ, from their 

 fancied resemblance to other objects, or from mistaken views 



* Op. citat. 



