CHA.PTEK V. 



OF SENSIBILITY IN GENERAL. 



HOWEVEE accustomed we may be to see the adage Natura non 

 facit saltus ceaselessly verified, and from whatever point we view 

 the world, to meet with graduated series of facts, we are compelled 

 to recognise in conscious sensibility a quality altogether peculiar, 

 manifesting itself suddenly, and without any link to connect it 

 with the other properties of inorganic or organic matter. With- 

 out doubt, there are degrees in sensibility. In following the 

 animal hierarchy, we see this property, at first confused, gaining 

 little by little in intensity, in clearness, then subdividing into 

 various departments ; but there is, nevertheless, a point where 

 sensibility abruptly starts up, for between unconsciousness and 

 consciousness there is no bridge. Here then we are in the pre- 

 sence of a new fact, quite as peculiar and unknown in its essence 

 as gravity is. But just as the want of any clear idea on the 

 subject of the inner nature of gravity has not hindered natural 

 philosophers from studying and formulating the laws of this 

 great property of matter, so, though ignorant as to what nervous 

 sensibility is in itself, we can indicate its modes and conditions. 



Conscious sensibility is a property inherent in certain nervous 

 fibres and cells. This is a general fact, which can be verified 

 from the highest to the lowest degree of the animal scale. Never- 

 theless, we must here point out the apparent exception in the 

 case of the infusoria. Many of them, in fact, according to the 

 evidence of our microscopes, have no nervous system, yet seem to 

 experience sensations. We see them move, to all appearance 

 voluntarily, avoid obstacles, &c., &c. Must we, to explain these 



