CH. III.] SENSATIONAL MOVEMENTS. 149 



the instinct, or bodily exercise, will develop fully (204). Con- 

 sequently, in this instinct the muscles contract, the limbs are 

 moved irregularly, and the animal often attempts to hop, leap, 

 soar, sit upright, &c., just as actually occurs during the grati- 

 fication of the instinct for corporeal -exercise ; and if there be 

 no extraneous impediment, it usually takes place instantaneously, 

 because a conception only, is enough to excite movement in the 

 voluntary muscles. In such cases, there results, in virtue of 

 the connection between the physical, mechanical, and vital 

 forces of the muscles appropriated to voluntary motion, the 

 further operations in the animal economy, such as a modification 

 of the fluids, promotion of secretion and excretion, increase 

 of muscular strength, and of the animal force itself (204), as is 

 the design of nature in the instinct. For details on the subject, 

 works on physiology may be consulted. {Vide Haller^s ^Phy- 

 siology,' § 11.) 



281. The instincts of animals for particular kinds of sensa- 

 tional voluntary movements, are easily understood from the 

 principles laid down in the previous paragraph. The instinct 

 for song of birds, which is usually a secondary instinct of the 

 instinct for propagation, arises from the sensational stimulus 

 of an unpleasant sensation in the chest, produced by changes 

 in the respiration and circulation resulting from the primary 

 instinct, as is also the case in man and other animals in 

 the acts of sighing, sobbing, weeping, moaning, talking, &c. 

 Every inducement of such external sensations, excites the 

 instinct of similar movements. Warmth, which accelerates 

 the movements and impedes respiration, stimulates birds to 

 sing even in winter, in heated rooms, and compels other 

 animals to sigh and pant [lechzen]. Wine, not less an ex- 

 citant of the vital movements, causes talkativeness ; a too crass 

 state of the blood causes melancholy, and weeping, sighing, 

 sobbing, &c. All these movements constitute generally the 

 satisfaction of the instinct itself, the proper sentient actions 

 of which are only previous imperfect manifestations of them, 

 as, for example, instead of singing, a frequent chirping; instead 

 of sighing, sobbing, or weeping, a deep inspiration ; instead of 

 speech, a mere sound, &c. To this class belongs also the 

 instinct of laughter in man, which is often secondary to other 

 agreeable instincts and sensations, and is also an accom- 



