CH. 1.] NERVE-ACTIONS IN GENERAL. 207 



sensations from non-conceptional internal impressions, and those 

 in § 148 imperfect external sensations from conceptional internal 

 impressions. It is manifested^ that the first of these may be 

 easily but erroneously confounded with the second. 



Note. — It may be permitted just to state here, a bearing 

 which these views have on pathology. Since the phenomena 

 mentioned, as arising from the causes aforesaid, may be excited 

 the more readily in proportion as the nerves are more sensitive, 

 and the conceptions vivid (148), it is obvious, why persons of 

 irritable temperaments and nerves, and patients in whom the 

 nerves are unusually susceptible of all kinds of impressions, 

 have those phenomena so frequently, and how erroneously they 

 are attributed to a too-vivid power of the imagination. * 



379. Now since, therefore, both the brain and sensory 

 nerves are endowed with vis nervosa, it must be understood, 

 that its actions are developed independently of the brain 

 (375, 358, 360), although they can be rarely rendered visible, 

 as they can scarcely communicate any visible movement (151) 

 to a mechanical machine. But it is quite otherwise with 

 [motor nerves ; and as almost all movements of animal machines 

 are either muscular movements, or effected by means of 

 muscles, or at least by muscular fibrils, the vis nervosa would 

 appear, although erroneously (375, 377), to be peculiar to 

 muscles and muscular fibrils only. This has probably given 

 rise to the new doctrine in physiology propounded by the 

 otherwise correct observer, Haller, who has laid down the 

 principle, that the muscular fibre possesses in itself a primary 

 animal motor force, which he has termed vis insita, muscular 

 irritability [die angeborne kraft], {Vide Haller's ^Physiology,' 

 § 400, 402.) It is, therefore, of importance to investigate the 

 subject, and see whether this opinion be well founded or not. 



380. To prove that the muscular fibre possesses an animal 

 motor force peculiar to itself, it must be shown to put itself in 

 action without the co-operation or assistance of other animal 

 machines or forces. A probable way of doing this, would be 

 to separate a muscle from all other animal machines, and then 

 demonstrate the existence of an animal motor force. But since 



j every muscle has its nerves (161), and is therefore connected 

 with animal machines, which enter -into its substance, and are 

 so intimately incorporated therewith and so constituting a 



