66 CEREBRAL FORCES. [i. 



common trunk of nerves altogether different, or even in the 

 spinal cord itself, which is the general stem of a great number 

 of nerves — equally reaches the brain at the point of origin of 

 the nerve which receives it, unmingled with any of the other 

 external impressions taking place at the same time, and in the 

 same direction, and there forms its own proper material ideas ; 

 so, also, the conceptional internal impressions travel from the 

 points in the brain in which they take place, along the nerves 

 arising from those points, and are propagated downwards through 

 the branches and terminating fibrils without being commingled 

 with other conceptional impressions taking place in the brain at 

 the same time, although they all pass together along one and the 

 same trunk, or rather first along the spinal cord to the larger 

 branches, and thence to the smaller branches and fibrils (124). 

 The cause of the two phenomena is identical (39) . The fibrils 

 of a nerve are already separated at its origin, and run each a 

 separate course as portions of the same larger nerve to their 

 allotted termination in the body (13). Each complete nerve 

 has, again, its special point of origin in the brain, and although 

 it passes downwards combined with many others into a large 

 trunk, such as, for example, the spinal cord, it is afterwards 

 given off again and remains distinct, and continues its own 

 special course to its final termination at the allotted spot. 

 Thus, consequently, an impression in the brain, made on the 

 origin of a nerve, or on one of its fibrils, takes its course along 

 the fibril, although ten other impressions may have been made in 

 the same nerve, or on other fibrils of the same nerve, and pro- 

 duces its results without being intermingled with the others. 



126. Although at the same time that conceptional im- 

 pressions are transmitted along a certain nerve-fibril, and by its 

 means perform their sentient actions, an external impression is 

 made on the same fibril, and takes its course upwards to the 

 brain along the same track, as far as the origin of the nerve 

 from whence the internal impression had set forth, still these 

 two impressions are in no wise interrupted in their course to 

 and from the brain, although opposed to each other, but each are 

 followed by their proper actions, as if the contrar}^ impression 

 had never been received (§§ 17, 18, Haller's ^Physiology,' § 377). 

 Is it not highly probable from this statement of facts, that some 

 of the numerous fibrils of which each nerve consists (17), are 



