CH. I.] ANIMAL NATURE IN GENERAL. 315 



by means of various external sensational conceptions, and 

 enumerated in § 611, those animal movements which, although 

 they can be, and often are, in unreasoning animals, mere nerve- 

 actions, can, nevertheless, be developed, arranged, and modified 

 by the cerebral forces solely (581 — 592). 



616. Reasoning animals, in addition to the preceding, are 

 capable of performing as sentient actions all movements vrhich 

 the higher emotions, intellectual pleasure or suffering, and 

 the desires, aversions, and satisfyings of the will develop 

 through the free-will movements; and this by means of the 

 cerebral force of the material ideas connected with the under- 

 standing and the will. And since these animal monements are 

 neither sensational actions, nor nerve-actions (336, 593), they 

 are the peculiar privilege of reasoning animals, and distinguish 

 them from all others. 



617. The animal nature (1) of an insentient animal is the 

 aggregate of its two kinds of vis nervosa : that of a sentient 

 animal is the aggregate of its two kinds of vis nervosa and its 

 cerebral forces ; and implies also the animal nature of the 

 insentient. The animal nature of a purely sensational animal, 

 is the aggregate of its two kinds of vis nervosa, and of the 

 cerebral forces of its sensational conceptions, desires, &c. The 

 animal nature of a reasoning animal is the aggregate of the 

 cerebral force of sensational and intellectual conceptions and 

 desires, &c., and presupposes the nature of the sensational 

 animal, which includes that of the insentient animal. 



618. The animal natures of all other animals are conjoined 

 in a reasoning animal, as well as the two essential principles 

 [principien] of all animal movements, namely, the vis nervosa 

 and the cerebral forces. The physician need not seek to explain 

 the mode in which the vis nei^vosa excites sensational concep- 

 tions and desires, and in which these, together with those of the 

 intellect, excite animal movements, for it is inexplicable : con- 

 sequently he need not investigate psychological explanations of 

 the union of body and soul; or the hypothesis of physicians as 

 to the nature of the vital spirits, of the medulla of the brain and 

 nerves, and of material ideas ; his business is with general facts, 

 from whence he must deduce his principles of theory and prac- 

 tice. The whole physiology of animal nature must be based 

 upon the following general principles : 



