PREFACE. lil. 
' degree, is the thraldom in which the Medical 
profession is held by Haller and Bichat; but 
neither the learning of the former, nor the elo- 
quence of the latter, will permanently maintain 
the popularity of opinions which are false in 
themselves, and destitute of every practical 
result. The great error of these celebrated 
writers on Irritability, consists in their apparently 
mistaking expansion of the fibrous texture in 
general, for mechanical elasticity; and contrac- 
tion, under all circumstances, for a state of 
increased action. When John Hunter speaks of 
muscular contraction, from the “ stimulus of 
death,” he uses language quite consonant with 
Haller and Bichat, but certainly at discord with 
Nature. 
In their aceount of Irritability, the action of 
the nervous system is set almost out of the 
question, while it is the principal agent con- 
cerned in all the motions of the fibres, whether 
voluntary or involuntary. The cause of Irrita- 
bility I have, in imitation of Gaubius, called 
the Vital Force, a term which is also used by 
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