[ 2l6 3 
made not upon the fibre, but upon the 
nerves of a given part, which in confe- 
quence throw the mufcular fibre into the 
Hate of contraction. 
It is in this fenfe that I call the blood 
the ftimulant of the heart, the aliment, 
air, gas and excrement the ftimuli of the 
inteftenal canal, the urine that of the blad¬ 
der, light the ftimulus of the Iris, and 
fo of the reft. 
Whenever the nerves feel a ftimulus, 
the electrical fluid is excited, and then its 
effects are made manifefL Under thefe 
circumftances that takes place, which we 
have noticed when fpeaking of voluntary 
motions, that is to fay, the electricity 
palling from one ftate to another, and 
changing its mode of exiftence, pro¬ 
duces the contraction. Its equilibrium is 
never eftablifhed. A new caufe again ex¬ 
cites this fluid, and another new effeCt 
takes place, which is relaxation. The 
electricity. 
