314 ANIMAL NATURE AS A WHOLE. [in. 



ments, for repose and playfulness, for combat, for self-defence, 

 for propagation of the species and care of offspring ; and of the 

 instinctive emotions, as rapacity, revenge, lasciviousness, and all 

 the passions closely allied to them (542 — 573). On the other 

 hand, the sentient actions of sentient animals, which arise as 

 free-will movements, from desires, aversions, and passions, de- 

 veloped in the mind according to psychological laws (564 — 573), 

 or from pleasing or displeasing conceptions of the understand- 

 ing, or from desires or aversions of the will (564, 576), cannot 

 be developed in insentient animals by means of the vis nervosa, 

 unless there be a sensational element in the conceptions them- 

 selves (578). 



612. Since sentient animals are endowed with the vis ner- 

 vosa, in common with the insentient, and which sometimes acts 

 in them alone, sometimes in connection and in harmony with 

 the cerebral forces, they are capable, under certain conditions, 

 of all those movements of which insentient animals are capable. 



613. Sentient animals are moved according to their nature, 

 not only by the vis nervosa, but by the forces of material ideas 

 in the brain. These material ideas are those either of external 

 sensations, and other sensational conceptions and desires, or of 

 intellectual conceptions : the former are regulated according to 

 the laws of the vis nervosa, the latter according to the psycholo- 

 gical laws of the conceptive force. By means of these cerebral 

 forces of conceptions, the movements iu sentient animals in the 

 natural condition are developed, arranged, and changed, in ac- 

 cordance with the conceptions in their mind : this, however, is 

 so done, that in purely sensational animals, and in the reason- 

 ing animals also, in so far as their sensational conceptive force 

 acts, the conceptions are caused and connected in the mind by 

 means of the vis nervosa of external impressions. On the other 

 hand, they arise and are linked together in rational animals, 

 when the conceptive force acts solely according to psychological 

 law (60, i, 579, i, ii). 



614. Purely sensational animals are capable of all the vital 

 actions just enumerated in § 600 (compare 161 — 179, 207, &c), 

 in virtue of the cerebral force of the sensational material ideas, 

 which external impressions excite and connect in the brain, and 

 which develop the vital actions as sentient actions. 



615. Purely sensational animals perform as sentient actions, 



