210 ANIMAL FORCES. [ii. 



The spring of a watch produces, by an invisible movement, 

 the visible movements of the wheels. But should the primary 

 force which sets them in motion be therefore attributed to 

 them? 



384. Haller observes, that it cannot be proved that from so 

 few nerves as are distributed in a muscle, so many fibrils can 

 arise as there are muscular fibrils; consequently the latter 

 cannot be considered as prolongations of the former. But this 

 is not necessary ; it is enough that every part of a muscle is 

 supplied with nerves, and that every muscular fibril, where- 

 soever irritated by the point of a needle, is sensitive. And 

 if, as Haller thinks, the nervous fluid communicates this irri- 

 tability, the fluid is derived through the nerves. 



385. Haller advances (§§ 402, 407), that animals without 

 brain, spinal cord, or nerves, such as polypes, are equally ex- 

 cited to motion by an irritant, and thus show that the structure 

 of the muscle alone is sufficient for animal movement. The 

 vital movements of plants lead to the same conclusion. 



The movements of plants, even those of the sensitive plant, 

 are regulated according to the mechanical laws of movement of 

 organised bodies. The fibrils in insects, which a touch excites 

 to animal movements, are not such nerves or muscles as ours, 

 but still animal machines (6), which are capable of receiving 

 external impressions (31, 32), whereby they stimulate the 

 mechanical machines of insects to animal movements (7, 162), 

 and, consequently, a species of motor nerves (14), and thus 

 aff'ord no proof of the existence of the primary motor force of 

 muscular fibre. 



386. The heart (it is advanced by Haller) and the intes- 

 tinal canal are regulated by the vis insita, or muscular force, 

 and by stimuli, for their movements are independent of the 

 mind, whilst the movements of the muscles actually dependent 

 upon the nerves are under the control of the will. 



The error here is very manifest : the great man has not 

 properly distinguished between sentient actions and nerve- 

 actions. If, 'according to Haller, when movements are excited 

 in muscles through their nerves, they must be excited in con- 

 nection with the brain, or the mind, or the will, then it follows 

 that animal movements excited after division or ligature of 

 the nerve going to the muscle, are not produced through 



