156 CORRELATION OF PHYSICAL FORCES. 



as have been adopted in this Essay might be applied to the 

 organic as well as the inorganic world ; and that muscular 

 force, animal and vegetable heat, &c. might, and at some time 

 will, be shown to have similar definite correlations ; but I have 

 purposely avoided this subject, as pertaining to a department 

 of science to which I have not devoted my attention. I 

 ought, however, while alluding to this subject, shortly to 

 mention some experiments of Professor Matteucci, communi- 

 cated to the Royal Society in the year 1850, by which it 

 appears that whatever mode of force it be which is propagated 

 along the nervous filaments, this mode of force is definitely 

 affected by currents of electricity. His experiments show 

 that when a current of positive electricity traverses a portion 

 of the muscle of a living animal in the same direction as that 

 in which the nerves ramify i.e. a direction from the brain to 

 the extremities a muscular contraction is produced in the 

 limb experimented on, showing that the nerve of motion is 

 affected ; while, if the current, as it is termed, be made to 

 traverse the muscle in the reverse direction, or towards the 

 nervous centres, the animal utters cries, and exhibits all the 

 indications of suffering pain, scarcely any muscular move- 

 ment being produced, showing that in this case the nerves 

 of sensation are affected by the electric current ; some defi- 

 nite polar condition therefore exists, or is induced in the 

 nerves, to which electricity is co-related, and probably this 

 polar condition constitutes or conveys nervous agency. There 

 are other analogies given in the papers of M. Matteucci, and 

 derived from the action of the electrical organs of fishes, 

 which tend to corroborate and develop the same view. 



By an application of the doctrine of the Correlation of 

 Forces, Dr. Carpenter has shown how a difficulty arising 

 from the ordinary notions of the development of an organised 

 being from its germ-cell may be lessened. It has been thought 

 by many physiologists that the nisus formativus, or organising 

 force of an animal or vegetable structure, lies dormant in the 

 primordial germ-cell. ' So that the organising force required 

 to build up an oak or a palm, an elephant or a whale, is con- 

 centrated in a minute particle only discernible by microscopic 

 aid' 



