PHYSIOLOGY. 



passions : we have therefore said, that weeping and laughing 

 are expressions of emotion and passion ; and in all these we are 

 conscious of some volition or propensity." 



In all these, as well as in the motions of No. 4., some volition 

 is concerned, not only as they can often be prevented by an- 

 other volition presenting itself, but, besides, as the several mo- 

 tions which occur in executing these propensities, are more or 

 fewer, and more or less forcible, according to the vehemence of 

 the propensity or effort. Very often the stimulus to these pro- 

 pensities is irresistible ; and, unless the peculiar stimulus is pre- 

 sent, the motions cannot be produced by any volition. 



6. By certain internal impressions arising from the exercise of 

 the functions of the body itself, which produce no sensation, nor 

 produce motions of which we are conscious except when exer- 

 cised in an unusual manner. Such are the causes of the mo- 

 tions of the heart and arteries, of the organs of respiration, of 

 the stomach, intestines, and perhaps of many other parts. 

 With regard to most of these motions, it may be supposed that 

 they are the mechanical effects of their several causes, acting 

 upon the inherent power of muscular fibres (LXXXVI.) ; but 

 it is sufficiently certain that they also depend upon an action of 

 the brain ; and the effects of passions, as well as the effects of 

 destroying or compressing the nerves of the organs concerned, 

 are proofs of it. 



The motions mentioned in this article are commonly suppos- 

 ed not to be accompanied with any volition of which we are dis- 

 tinctly conscious. This, perhaps, is not strictly true with re- 

 gard to most of them ; and, so far as it is, it may be imputed to 

 that repetition which destroys consciousness, (LV.). But neither 

 can we entirely adopt this explanation ; as these motions, 

 which are intended to follow one stimulus only, may be sup- 

 posed to require no exercise of volition, as in the case of the 

 heart, arteries, and alimentary canal, while the action of respi- 

 ration, as adapted to various purposes, continues to be a volun- 

 tary motion. 



7- By various occasional impressions of external bodies, and 

 by various occasional states of the system, or of its particular 

 parts, which excite motions not only in the parts to which the 

 impressions are immediately applied, but also in distant parts 



