SYSTEMATIC SYNTHESIS OF TISSUES INTO ORGANS. 267 



found in large masses of white fibres, it is not supposed 

 to be great. 



622. Remark. The special nerves may best be described as parts 

 of apparatus. 



SECTION IV. 



Ganglia. 



623. GANGLIA are organs designed to excite activi- 

 ty (of mind, of muscle, of the secretory tissue), the es- 

 sential part of which is cells, in which the power of ex- 

 citing activity is developed. 



624. THE CELLS OF GANGLIA ARE PRODUCED in the 

 midst of a granular substance, and are connected with 

 the nervous fibres, through which the cells act and are 

 acted upon. 



625. How THE CELLS ACT, or how they are acted 

 upon, is not understood ; it is said to be by nervous in- 

 fluence, but what that is, or how produced, or how it 

 acts, is not known ; it is so called because it acts through 

 the nerves, and they are concerned in and essential to its 

 action. 



626. Whether THE NERVOUS INFLUENCE is ALWAYS 

 ONE THING, or whether it varies according to the circum- 

 stances under which it acts, is not known ; it is only 

 certain that in some way it produces different effects in 

 different cases. 



627. It is ALSO CERTAIN that the exertion of this in- 

 fluence, either upon or from the cells, is attended by a 

 change in them, requiring their nutrition in harmony 

 with their action. 



628. THE GANGLIA MUST ALSO BE CONSTRUCTED of 

 fine fibres of sinewy tissue woven through and around 

 them, and if they have any free surfaces liable to fric- 

 tion they must be covered with secretory tissue ; and to 



628. What are ? 624. How are ? 625. How ? 626.1s? 627. What 

 Is ? 628. How must ? What tissues in ? 



