70 



to occasion various sensations ?" The latter suppo- 

 M r ion is wholly overthrown by the phenomena of 

 wounded nerves. A nerve cut asunder, does not re- 

 tract its divided extremities, but becomes rather Ion- 

 ger,extruding its medulla into around tubercle. Again, 

 were it elastic, it should be composed of hard fibres, 

 having their extremities fixed to soine firm bodies : 

 since strings, otherwise constituted and disposed^ 

 have no elasticity. But it is evident all nerves are 

 soft at their origin, as well as void of tension, and 

 some soft in every part, as the olfactory nerve, and 

 the soft portion of the auditory nerve. Yea, they 

 all grow soft in the viscera, the muscles, and the sen- 

 sories, before they exert their functions. Besides, 

 some nerves are so situate, that they cannot vibrate, 

 as those of the heart, which are fastened to the great 

 vessels and the pericardium. Further, the influence 

 of an irritated nerve is never propagated upwards; 

 whereas an elastic chord communicates its tremors to 

 both ends from the point of percussion. Hence it is 

 plain the nerves do not act by their spring, but by 

 the motion of their proper fluid. The extreme small- 

 ness of these canals, which no microscope can reach, 

 is no valid objection to this, neither our inability to 

 discern tliat fluid. This only proves the imperfection 

 of our senses. 



" But what is this fluid?" Who can tell? We 

 may very probably conjecture, it cousists of some 

 subtle fire or ether, diffused through the whole sys- 

 tem of nature, and acting by laws unknown to us. 



51. Of the other fluids, some serve to prepare the 

 diyle, some to thin .the blood and preserve it from 

 putrefaction. Others only remain till they can be 

 thrown out of the body, as being useless and super, 

 fluous. All of these, but the chyle, arise from the 

 blood, being secreted from it by proper glands. But 

 as to the manner of secretion, after all the most ac- 

 curate and laborious enquiries, it still remains aoso- 

 lutely uncertain, and every oce abounds in his own 



