OPINIONS OF HALLER. 495 



pressing passions, &c. diminish the vital energy 

 of the brain, and through it that of all the other 

 organs, causing debility and a spasmodic state of 

 the capillary vessels, as in the cold stage of fevers. 

 He further maintained that the temperature of 

 animals is in proportion to the quantity of their life, 

 or nervous energy. Yet he never explained how 

 animal heat is generated by respiration ; how 

 diminished during the cold stage of fever, and 

 increased during the hot ; why fever is attended 

 with nausea, headache, pains in the back, limbs, 

 &c. ; nor in what way spasmodic diseases arise 

 from derangement of the nervous system. But 

 I shall endeavour to make it clear in the fol- 

 lowing pages, that the brain is no more the 

 origin of animal motion, than the rudder of a 

 steam-vessel is the cause of its moving power ; 

 that as the object of the one is to guide the di- 

 rection of the vessel, so is it the office of the other 

 to generate ideas, or endow the living machine 

 with sensation, intelligence, volition, &c. 



In accordance with the Newtonian doctrine, 

 that all the molecular changes of matter are 

 owing to the innate powers of attraction and re- 

 pulsion, Haller referred the phenomena of life to 

 irritability and sensibility, the first of which was 

 regarded as an inherent property of the mus- 

 cular fibre, and termed vis insita ; while the 

 other was supposed to reside in the medullary 

 tissue, and was called the vis nervosa. But if the 

 muscular and nervous systems be riot duly sup- 



