CH. v.] SYSTEM OF THE FORCES OF ANIMAL LIFE. 339 



the nervous system cannot, either wholly or in part, perform its 

 functions, independently of any defect of structure; as, for 

 example, before the animal has an independent existence. It 

 is also a mistake to refer the true animal functions solely to 

 the structure of the animal, since that only renders the func- 

 tions possible. But while the accomplishment of the functions 

 by the animal forces implies the existence of the requisite 

 structures, the absence or injury of the structures, and every- 

 thing which renders them incapable of performing their func- 

 tions, interrupts life, and brings it to a termination. Thus, if 

 the brain be removed or destroyed, sensational life ceases ; and 

 animal life would cease too, if all the nerves were destroyed, or 

 all the vital spirits, or their circulation through the nerves en- 

 tirely arrested, or any means used by which the nerves were 

 rendered unfit to receive any impression, although the same 

 impressions may still be made, which make ordinary circum- 

 stances constitute true animal motor forces (356). 



665. The animal forces, which give vitality to the whole 

 animal kingdom, are all those impressions of which animal 

 machines are capable, in virtue of their proper animal structure. 

 These impressions have been already fully considered, as well 

 as their co-ordinate and reciprocal action (31, &c., 121, 356, 

 590, &c.) We must, however, note more specially their mutual 

 subordination, or their dependence on each other. 



666. An animal function (the action of an animal force) 

 which is based on another, is subordinate to it (Baumgarten^s 

 'Metaphysics,^ § 25). Consequently, this subordinate function 

 implies another animal function and force, namely, that to 

 which it is subordinate. Now, as many animal functions are 

 based on others, as, for example, sentient actions or imagina- 

 tions, these latter on sensations, and sensations on external 

 impressions, there is doubtless a subordination of animal forces 

 in animal life; and if they can act in the natural condition in 

 no other way than subordinately, it is a natural subordination} 



667. There are certain animal forces which are not naturally 

 subordinate to any others, namely, — i. External impressions 

 when not in themselves animal actions ; for the nerves receive 



' The term natural has here and elsewhere a peculiar meaning, and refers to the 

 mode of action of the organism, as resulting necessarily from its organisation. See 

 note to § 27.— Ed. 



