82 PHYSIOLOGY. 



that the irritability of the muscle was at length lost, and that 

 stimuli no longer had their effect. Haller would willingly doubt 

 the accuracy of these experiments, but he is obliged to say, in the 

 conclusion, that we must acknowledge that there is a diminution 

 of the irritability by a ligature. Therefore the animal power 

 is not only necessary to voluntary contraction, but even to the 

 irritability, to the affection of the inherent power by stimuli. 

 How soon do the passions of the mind enervate, weaken the tone, 

 and give a certain insensibility to the action of every stimulus 

 applied in order to move the muscles ! We will hardly doubt 

 that the ordinary inherent power is in some dependence upon 

 the animal and nervous ; which is, I think, confirmed by what 

 Haller allows, that the effects of the inherent power, in conse- 

 quence of stimuli applied to muscles, are remarkably weaker 

 than those that are exerted by the force of the animal power. 

 Here is an experiment for showing the force of the inherent 

 power considered by itself : if I just now support my arm and 

 bend the cubit in this manner, I find that the biceps muscle is 

 contracted; it is fuller and a little firmer in its middle part than 

 it is when in an extended state ; but it is not so much so as when 

 I make the flexion by internal force, and give an opportunity to 

 the muscle to contract. When this contraction is only made by 

 its inherent power it is still flaccid ; but, taking away the support, 

 and continuing the arm in that position by means of the animal 

 power, the biceps immediately grows remarkably harder and 

 fuller than it was before ; and in every other experiment which 

 we can make to this purpose the same appears. I would say 

 that the vigour of the inherent power cannot be evident in a 

 living animal, because we cannot be certain of its acting entire- 

 ly without the nervous power ; and with regard to the strength 

 with which that muscle contracts, I can undertake to show that, 

 in different conditions of the body, as it is weakened by disease, 

 or various other causes, or as it is again increased by powers 

 which have that effect, this very contraction will be perceived to 

 be manifestly different ; and that the tone of the inherent power 

 is increased or diminished by causes acting upon the brain, and 

 upon the brain alone, I shall have many occasions to prove. I 

 shall give one illustration at present. In the case of mania, it 

 is well known that men can exert a force vastly greater than any 



