68 CEREBRAL FORCES. [i. 



are distributed to various organs of the body, it follows that 

 some of its fibrils that transmit the impression from the brain 

 downwards may go to one tissue, and some of those which 

 transmit the external impression upwards again into other 

 tissues widely distant, and thus a sensation in a limb trans- 

 mitted along the same principal nerve, may, by means of the 

 cerebral impression, develope a sentient action (movement) in 

 limbs far distant from the point of irritation. This connection 

 between the sentient actions of various parts is termed the 

 sympathy of sentient actions. When the fibrilli of a nerve 

 which transmits external impressions to the brain, to pro- 

 duce corresponding material ideas at the point of its origin 

 in the brain, have experienced some injury at its origin, being 

 compressed or stretched, for example, in such a way, that those 

 fibrilli only have their function interrupted which transmit the 

 cerebral impression downwards, — the consequence is, that the 

 sentient action (as, for example, a voluntary motion), which 

 formerly resulted from this external sensation (excited by the 

 material idea in the brain), ceases to be excited, until the 

 impediment is removed. Thus, it is intelligible, how a nerve 

 may retain its sensibility and yet have lost its motor power ; 

 being sensitive and yet paralysed, as is often observed. If, on 

 the other hand, the obstruction involves those fibrils only at 

 the cerebral origin of the nerve which transmit the external 

 impression to the brain, the latter will develope no material 

 idea in the brain and no sensation in the mind ; but a sponta- 

 neous conception can excite a material idea (an internal im 

 pression) at the origin of the nerve, and this may be transmitted 

 along the fibrils, and produce actions in the body, such as a 

 voluntary movement, for example. In other words, the same 

 nerve may be insensible, and still the channel of the will. 

 How could it be possible to explain these two classes of phe- 

 nomena, if the existence of this diff*erence in the fibrils of the 

 same nerve be not admitted ? It is manifest to every one, that 

 the nervous fibrils are distinct and separated from each other 

 at their origin. From these and other considerations, which 

 will be stated subsequently, this doctrine of two distinct classes 

 of nerve-fibrils existing in the same nerve, and which are appro- 

 priated to the two kinds of internal and external impressions 

 respectively, acquires an air of truthfulness which renders it 



