*as of two sorts of motion 5 a sensibility in virtue of which, certain parts 

 can send up to the brain, the impressions they receive, to be there objects 

 of consciousness ; and another sensibility belonging to all organs without 

 exception, and all that some of them possess, which is sufficient for the 

 exercise of the functions f nutrition, and by means of which they are 

 evolved, and kept up in their natural state ; two kinds of contractility, 

 appropriated to the two different kinds of sensibility: The one, in vir- 

 tue of which the muscles obedient to the will, exercise the contractions 

 which it determines; the other, independent of the will, manifests itself 

 by actions, of which we have no intimation, any more than of the im- 

 pressions by which they are determined. 



The distinction being fairly laid down between sensibility and contrac- 

 tility, it is easy to understand the origin of the endless disputes of Haller 

 and his followers, about the parts of the body, in man and animals, which 

 are endowed with sensibility and t irritability. All the organs to which' 

 that learned physiologist has denied these properties, as bones, tendons, 

 membranes, cartilages, and cellular membrane, &c. possess only that 

 latent sensibility, and that obscure contractility, common to all living 

 beings, and without which, it is impossible to conceive life to exist. In 

 a state of health, they are utterly incapable of transmitting to the brain 

 perceptible impressions, and of receiving from it the principle of mani- 

 fest and sensible motion. It has likewise been a matter of much dispute, 

 whether sensibility and contractility are qualities, of nerves; if these 

 parts are their only instruments, and if their destruction is attended with 

 a loss of these two vital properties, in the parts to which they are trans- 

 mitted. We may answer in the affirmative, as far as relates to the sensi- 

 bility of perception, and the voluntary motion which is entirely subser- 

 vient to it, but that the existence of nerves is not at all necessary to the 

 exercise of the sensibility and contractility which are indispensable to 

 the assimilation of nutrition. 



No part'of the living body is absolutely insensible, but that sensibility 

 of every organ is so modified, that it is not affected by the same stimuli. 

 Thus, the eye is insensible to sound, and the ear to light. A solution of 

 tartar emetic, causes no disagreeable impression to the conjunctiva; 

 taken into the stomach, it excites convulsive motions, while an acid from 

 which the stomach does not suffer, proves a cause of irritation to the con- 

 junctiva, and brings on a violent inflamation of the eye. In the same 

 manner, purgatives pass along the stomach, without producing any ef- 

 fect on the viscus, but they stimulate the alimentary canal. Cantharides 

 have a specific action on the bladder; and mercury on the salivary 

 glands. Eacn part feels, lives, moves, after its own way 5 in each the 

 vital properties appear under such shades and modifications, that they 

 may be looked upon as so many separate members of the same family, 

 concurring in one endeavour, working for a common end, consentientia 

 omnia. (Hipp.) 



The faculty of assigning a cause to the sensation, and that of moving 

 by volition, which man possesses in common with all animals formed 

 with a distinct nervous centre, are essentially bound together. For sup- 

 pose a living being, furnished with locomotive organs, but without sen- 

 sation, placed in the midst of bodies, that every moment endanger its 

 existence, without any means of distinguishing them, it will hasten its 

 own destruction. If perceptibility could, on the other hand, exist inde- 

 pendently of motion, how dreadful would be the fate of such sentient be- 



