CHAPTER II. 



THE ANIMAL FORCES CONSIDERED ABSTRACTEDLY, AND 

 PARTICULARLY AS ANIMAL-SENTIENT FORCES. 



16. To what end are the animal forces peculiar to the 

 animal machines only, without reference to their influence on 

 the other portions of the organism, so that the latter would 

 still possess them, even if not united with the mechanical 

 machines which move the body? The answer to this question 

 is the object of the present chapter. 



SECTTON I.— THE FUNCTIONS OF THE VITAL SPIRITS. 



17. The vital spirits originate in the brain (11). If, con- 

 sequently, they contribute, in some degree, to the functions of 

 the nerves, and are present in them, or carry the impressions 

 made on the brain from time to time along the trunks, twigs, 

 and terminating fibrils of the nerves, they must flow from the 

 brain to the most remote termination of the nerves, or, at 

 least, propagate the impression on the brain in this direction, 

 namely, downwards to the termination of the nerves; and have 

 also a natural motion from the brain downwards along the 

 trunks, branches, and terminating fibrils of tl^e nerves, whereby 

 they become the medium of the direct action of the brain on 

 the nerves (122). 



18. If the vital spirits already secreted in the nerves con- 

 tribute somewhat to the functions of the brain, and carry to 

 it the impressions received from time to time by the termi- 

 nations of the nerves (11), they must also flow from the latter 

 to the former, or at least propagate the external impression 

 in that direction upwards to the brain, and possess a natural 

 motion from the terminating fibrils of the nerves upwards to 

 the brain, whereby they become the medium of the direct action 

 of the nerves in the brain (36 — Haller). 



19. This interposition of the nervous fluid between the re- 



