ANATOMY OF THE NERVOUS TISSUE. 17 



are important and essential in the transmission of the special 

 impressions to the terminal branches of the nerves. 



In treating of the nervous system, we will consider first 

 the physiological anatomy of the nervous tissue ; next, the 

 general properties of the cerebro-spinal system ; next, the 

 functions of different portions of this system connected with 

 motion, ordinary sensibility, intellection, etc. ; next, the func- 

 tions of the sympathetic, or organic system of nerves ; and 

 finally, the special senses, with the physiological anatomy 

 and mechanism of the accessory parts. 1 



Physiological Anatomy of the Nervous Tissue. 



The physiological anatomy of the nervous system natu- 

 ally divides itself into two sections ; one embracing what is 

 called the general anatomy of the nervous tissue, and the 

 other, the arrangement of this tissue in special organs, as 

 far as this is connected with their functions. 



The intimate structure of the different portions of the 

 nervous system may now be regarded as tolerably well un- 

 derstood, at least as far as those anatomical points bearing 

 on physiology are concerned. The connection between the 

 nerve-cells and the fibres and the modes of termination of the 

 motor filaments in the muscles are points nearly, if not quite, 

 settled ; and the terminations of sensory filaments in integu- 

 ment and mucous membranes have lately been investigated 

 very thoroughly, and with quite positive and satisfactory re- 

 sults. These anatomical points are especially connected with 

 the general properties of the nervous system, both as a gen- 

 erator of the so-called nerve-force and as a conductor. 



The arrangement of the nervous elements in special or- 

 gans, as in the brain and spinal cord, has not been so suc- 

 cessfully investigated, and presents immense difficulties in 

 its study ; and we can hardly hope to acquire any thing like 



1 The special senses will be fully considered in the fifth and last volume of 

 this series. 



