Vital and Physical Motion. 1 1 9 



little shifted since the days of the schoolmen, when 

 occult qualities of one kind or another were thought to 

 be a sufficient explanation for everything when, for 

 example, terreity, aqueity, and sulphureity, the occult 

 qualities of the three elements, earth, water, and sulphur, 

 of which, in varying proportions, according to Paracelsus, 

 all bodies are composed, were supposed to account for 

 all that was general in these bodies, when Petreity was 

 thought to be a sufficient explanation of the peculiarities 

 distinguishing Peter from Paul or other men, when the 

 answer of Argan* to the question, ' quare opium facit 

 dormire,' in the mock examination for the diploma of 

 physician, would have been listened to without a smile 

 if it had been given in sober earnest before the exa- 

 miners of a real faculty of medicine : 



Mihi a docto doctore 

 Demandatur causam et rationem qnarc 

 Opium facit dormire. 

 Et ego respondeo 

 Quia est in eo 

 Virtus dormitiva 

 Cujus est natura 

 Sensus assoupire. 



For in referring vital motion to a property of irrita- 

 bility, what more is done than to say, that the moving 

 body moves because it is actuated by an occult quality 

 which is suspiciously akin to terreity, aqueity, or sul- 

 phureity, or to Petriety, or to the 'virtus dormitiva' of 

 opium in the comedy ? ' To tell us,' as Newton said, 

 ' that every species of thing is endowed with an occult 

 specific quality is to tell us nothing: ( Even to say that 

 the phenomenon is vital, is, as Whewell remarks, ' very 



* Moliere " La Malade Imaginaire : ' 3ieme interlude. 



