144 ANIMAL.SENTIENT FORCES. [i. 



iii. The effort of the animal-sentient forces to develop the 

 complete sensation wherein the sensational stimulus is (272). 



iv. The sentient actions of all subordinate conceptions (273, 

 274). 



V. The development of the complete sensation, or the 

 satisfaction of the instinct, when it is fulfilled, for which, in 

 the true instincts, an external impression is requisite, and 

 which impressions themselves excite actions (275). 



Since the mind cannot voluntarily satisfy the greater number 

 of the instincts, but must await to this end an external im- 

 pression, which cannot possibly occur immediately (276, i), we 

 can understand the reason, why the instincts and all other 

 sensational desires and aversions in general, to which an ex- 

 ternal impression is necessary for their satisfaction, often require 

 so long and fruitless an effort of the mind, and such a com- 

 bined effort of the animal sentient forces ; while others, as the 

 instinct to voluntary movement (283), and the desires and 

 aversions of the will, are much calmer, and are satisfied, 

 apparently, with much less effort of the mind and motor forces; 

 for a limb may be moved, as soon as the motion is willed. 

 In the latter class, the satisfying sensation is not an external 

 sensation, but a spontaneous conception of the mind, to the 

 perfect development of which no external impression on the 

 nerves need be awaited. {Vide 336). 



278. We have now to consider the instincts in detail, in 

 accordance with this general view: with the object of inquiring 

 in what mechanical machines each kind manifests sentient 

 actions ; to what end these are manifested ; according to what 

 laws; and what is the great result they have in the animal 

 economy by means of the connection between the physical, 

 mechanical, and animal forces of the part in which they act. 

 But since each sensational instinct may be numerously sub- 

 divided, we will take only the chiefest into consideration, so as to 

 give the elementary principles of a more detailed doctrine 

 respecting the actions of the instincts. 



279. The sensational instincts of self-preservation and self- 

 defence, may be classed together in reference to their objects 

 and natural intent, namely, the preservation and well-being 

 of the animal, and the modes in which those objects are 

 attained (262) . In this class, indeed, we place the instincts of 



