CH. v.] SYSTEM OF THE FORCES OF ANIMAL LIFE. 341 



prolongations of it, and the current of the vital spirits passes 

 upwards and downwards in both (21) ; in others, all the animal 

 lachines are in general connection, by means of ganglia, 

 )ranches, and plexuses. Nevertheless, every portion of the 

 lystem of animal machines is of itself capable of animal forces 

 (31). The brain receives its own impressions at points quite 

 .different from those at which the external impressions which 

 are felt are received (124) ; as well as those from other con- 

 ceptions (130, i). In like manner, every nerve, every portion 

 of the system of nerves, has the capability of receiving both 

 internal and external impressions, and when there are no na- 

 tural obstacles present, of transmitting them to other branches, 

 or other nerves, either through the ganglia or plexuses, or com- 

 municating nerves, or through the brain itself, by means of 

 conceptions (31, 32, 121). But if the action of an animal force 

 in this system of animal machines shall have another subordinate 

 to it, it must excite another animal force either in the same 

 portion of the system — as when an external impression excites 

 an internal impression in the same nerve, or vice versa; or else 

 it must excite an animal force in another portion — as when an 

 external impression on one nerve excites either an internal or 

 external impression in other nerves, or other branches, &c. 



672. This natural subordination of the animal forces does not, 

 therefore, occur in each and every point of the system of animal 

 machines, but (as experience proves) certain points are destined 

 by nature to this end ; these may be termed the natural con- 

 necting points of the animal forces, inasmuch as in these the 

 forces communicate and combine with each other. The external 

 impression continues its course along the nerve, until it arrives 

 where a branch is given off, and which receives it as an internal 

 impression, and thereby other animal actions may be produced ; 

 or until the nerve is intermingled with others in the ganglia 

 or plexuses, where its external impression can be received, and 

 act as an internal impression (421) ; or in sentient animals, 

 until the external impression reaches the origin of its nerve in 

 the brain, and there, by means of a conception (sensation), 

 excites the animal-sentient force to send it back again along 

 the nerve (35, 121, 124) ; or until one of its nerve-actions 

 excites external impressions, which cause corresponding sensa- 

 tions and sentient actions (184, i, 443). An internal impres- 



