cu. I.] ANIMAL NATURE IN GENERAL. 311 



our definition is based on the condition, that the organism be 

 entire, and in its natural state. A decapitated animal is a 

 living animal body, and not a living animal. 



603. A living animal is regulated in its natural state by the 

 animal moving forces of its own animal machines. These are 

 the analogues of our nerves and our brain, at least we know 

 of no other; and their animal forces are the impressions of which 

 they are susceptible, when touched, or when a movement is 

 communicated to them (31, 32, 121). Further, every living 

 animal is regulated, either by the vis nervosa, or by the cere- 

 bral forces, or by both (356) . If by cerebral forces, then it is 

 by means of external sensations and conceptional impressions 

 (65, 121), and, consequently, also by the vis nervosa of the 

 external and internal impressions (35, 32, 358, 360). That the 

 vis nervosa alone regulates living animals is fully proved in the 

 Second Part. Now, since the cerebral forces imply the action 

 of a conceptive force, or mind, it follows that the animals 

 endowed with the former have also the latter, or are sentient 

 animals; while those which are regulated solely by the vis 

 nervosa are insentient, or simply living animals. 



604. Every insentient animal must possess nerves, or their 

 analogues, to which the vis nervosa is adapted by nature. But 

 since their external impressions are not felt, and their internal 

 impressions never produced by conceptions, and as they require 

 no animal sentient forces, it follows, that in so far as the brain 

 is the seat of the latter, and of mind, or the conceptive force, it 

 may be entirely wanting, and yet they may perform all the 

 acts necessary to their existence. 



605. Every sentient animal must not only be endowed with 

 mind, or the conceptive force, but also with the vis nervosa 

 and nerves, and with the cerebral forces and a brain : if the 

 soul be spiritual, that is to say, if the animal be endowed with 

 understanding and will (574), it is termed a reasoning animal, 

 but if the soul be simply sensational, then the animal is a 

 sensational or unreasoning animal (a brute) . 



606. Insentient animals are moved solely by means of the 

 nerves; and if, also, in sentient animals, the cerebral forces do not 

 act, still the greater number of their vital movements, natural 

 functions, and sentient actions, can be produced by the vis 

 nervosa ; and when in such the brain does co-operate, it is by 



