071 Muscular Motto Ji and Animal Spirits 283 



affected by the heat of the lamp ; but that con- 

 traction of the string is not produced in the common 

 way, but the string seems to undergo a spontaneous 

 movement, and to run together into itself in the 

 manner of fibrils — a very pleasant sight. But if the 

 contracted string be removed from the lamp it can 

 be drawn out to its former length with very little 

 effort. As to the cause from which the contraction 

 of the string proceeds, we may believe that the nitro- 

 aerial particles, bursting out of the flame of the lamp, 

 produce that contraction of the string ; for we have 

 elsewhere shown that igneous particles of any kind 

 (and it is by them that the said string is contracted) 

 are nothing else than nitro-aerial particles in a state 

 of motion. But the contraction of the string seems 

 to proceed from its being twisted by the nitro-aerial 

 particles : for if one end of the cord is left free, or if 

 it is held less firmly between the fingers and brought 

 towards the lamp, we shall see the cord rotated 

 pretty quickly. For as the nitro-aerial particles 

 bursting out of the lamp with the circumgyratory 

 motion proper to them act on the said cord, they 

 drive it round with their own motion and twist it. 



And it is certainly probable that the contraction 

 of the fibrils is accomplished in a not very dissimilar 

 way : for the fibrils, in which the contraction primarily 

 takes place seem, in as far as the microscope can 

 help us, to be very like an extremely slender music 

 string. Besides, we suppose that the contraction of 

 the fibrils is caused by nitro-aerial particles set in 

 motion, and even pretty intensely warmed in the 

 motor parts. Wherefore, if a coarse and thick cord 

 undergoes contraction when touched by nitro-aerial 

 particles, how much more should the extremely 

 slender fibrils, fashioned with the highest skill, follow 



