ON THOUGHT IN MEDICINE. 215 



no mere than that the nerves, as concerns the changes 

 which take place in them after excitation, are in an 

 exceedingly unstable state of equilibrium ; this was 

 looked upon as the fundamental property of animal 

 life, and was unhesitatingly transferred to the other 

 organs and tissues of the body, for which there was no 

 similar justification. It was believed that none of 

 them were active of themselves, but must receive an 

 impulse by a stimulus from without; air and nourish- 

 ment were considered to be the normal stimuli. The 

 kind of activity seemed, on the contrary, to be con- 

 ditioned by the specific energy of the organ, under the 

 influence of the vital force. Increase or diminution 

 of the excitability was the category under which the 

 whole of the acute diseases were referred, and from 

 which indications were taken as to whether the treat- 

 ment should be lowering or stimulating. The rigid 

 one-sidedness and the unrelenting logic with which 

 Robert Brown had once worked out this system was 

 broken, but it always furnished the leading points of 

 view. 



The vital force had formerly lodged as ethereal 

 spirit, as a Pneuma in the arteries ; it had then with 

 Paracelsus acquired the form of an Archeus, a kind 

 of useful Kobold, or indwelling alchymist, and had 

 acquired its clearest scientific position as ' soul of 

 life, oni^rta inscia, in Georg Ernst Stahl, who, in 



