xii TRANSLATOR'S INTRODUCTION. 



contraction of the pupil, so as to exclude the too vivid light from the 

 eye, and obviate its unpleasant impression." 



Prochaska then adds other illustrations, which he explains 

 in a similar manner; namely, the closure of the eyelids when 

 a finger is brought near to the eye ; the act of sneezing, from 

 irritation of the nostrils ; of coughing, from irritation of the 

 bronchi; the increased action of the heart and arteries, from 

 the presence of a poison or other irritating materies in the 

 blood, " whereby the blood is circulated more rapidly, and all 

 the powers of those structures are called forth, as it were, to 

 diminish the irritation, to render it harmless, or to expel it 

 from the organism.^^ He then proceeds : 



" § 220. These adduced examples sufficiently show that the sen- 

 sorium commune acts, in all its operations, strictly according to the 

 law of self-conservation, and that it is ever studious to do the best for 

 our preservation, so long as it is not prevented by disease, or the 

 cessation of vital action ; in which cases it is seen that it is thrown 

 into confusion, and no longer always takes the best steps for the cure 

 of disease ; often, indeed, proving itself altogether incompetent thereto ; 

 just as a delirious or idiotic person, from the disordered state of his 

 soul-sensorium, neither knows what is necessary to his preservation, 

 nor does it." ^ 



In his details, we find Prochaska repeating several of the 

 views of Unzer, although they are mixed up with opinions 

 derived from the writings of others, or his own researches. 

 He thus notices an important distinction between the two 

 great classes of involuntary and voluntary acts : 



** § 175. Nevertheless, this need for rest seems only to be a charac- 

 teristic of the nerves which are subordinate to the will, and not to the 

 involuntary, which have to provide for the motion of the heart, respi- 

 ration, and digestion ; and whose vis nervosa is active, without inter- 

 mission, during the whole of life, although it may be weaker or 

 stronger. Though it cannot be doubted that both kinds of vis have a 

 similar origin (§§ 171, 173), and are of the same nature, still obser- 

 vation shows, that the one belongs to the will, the other is involuntary ; 

 that the former is exhausted by sensation and motion, and requires 

 rest and repose ; with the latter, the contrary takes place ; and, finally, 

 that the two kinds of vis are independent of each other. This dis- 



' Op. cit. 



