REPORT ON ANIAIAL PIIYSIOI.O(- Y. 103 



brains, which continually supply the parts to which they distri- 

 bute their nerves with new impulses and fresh activity, without 

 immediate dependence upon the brain ; and that hence it is that 

 the vital functions are continued when the influence of the brain 

 is suspended, as in sleep or in paralysis. These opinions of 

 Johnstone respecting the ganglia were the foundation of that 

 hypothesis respecting the nerves of organic life which represents 

 them as a system distinct from the cerebral system, and which, 

 more fully developed by Bichat and by Reil, was pretty gene- 

 rally received from them by physiologists, until it was shaken by 

 the discoveries of Le Gallois and Wilson Philip. 



In this way the physical and dynamic theories came to be vari- 

 ously combined. Their union gained its greatest perfection under 

 Hoftmann and under Boerhaave, who insisted upon the primary 

 influence of the nervous system in modifying and regulating all 

 the organic functions, whether performed chemically or mechani- 

 cally. Thus nervous power came to be considered as nearly 

 equivalent to the anima of Stahl. But Stahl's system was not 

 improved by the change; for nervous power, a manifestation of 

 the vital energy by means of the peculiar matter of the nervous 

 system which that energy has produced, and of which it is but a 

 partial effect, cannot properly represent the entire cause ; and it 

 affords no explanation of the organic life of plants. For the vital 

 principle appears to manifest its several activities by means of 

 the organs which it has produced : and Stahl's error seems to 

 have been that he connected its vegetative processes, which are 

 defined and necessitated, with those of consciousness and intel- 

 ligence, which are free, and are developed only with the develop- 

 ment of the brain*. 



The age of Haller, at which we have at length arrived, is the 

 epoch from which modern physiology takes its date. The great 

 object which that eminent person endeavoured to achieve, was 

 to discover, experimentally, the conditions and the laws which 

 govern those vital phsenomena which the assimiption neither of 

 mechanical nor of chemical forces had been able to explain, and 

 thus to I'ender physiology as certain as other physical sciences. 

 For this purpose he excluded those metaphysical subtleties by 

 which his predecessors had so frequently veiled ignorance ; ex- 

 cluded also mathematical and chemical science in all cases in 

 which it was impossible to ascertain the elements upon which 

 their application could be founded. He was \villing, as he liim- 

 self says, to confess himself ignorant of the manner in which the 

 soul and body are united, and was content to proceed no further 

 than those discoverable laws which the Creator has himself pre- 



* Miillcv, Physiologie. 



