108 THE MICROSCOriST. 



tions of volition and sensation, that the nerves should be sup- 

 plied with the proper vital stimulus of the organization the 

 blood and the mode in which this stimulus is supplied, will 

 determine the character of the impressions made upon, or 

 received by, the entity or being referred to. 



This entity, which some have confounded with the vital 

 principle, acts through the nerves in a manner peculiar to itself. 

 The force or material by which it holds connexion with the 

 bodily frame is not electricity, although in some respects its 

 properties are analogous. Messrs. Todd and Bowman present 

 the following arguments, which prove conclusively the last re- 

 mark. They show that the electric fluid could not be suffi- 

 ciently insulated in the minute nerve-tubes to enable them to 

 be proper conductors that the most delicate tests of electricity 

 fail to discover it, when applied to nerve in action that a 

 ligature to a nerve stops the propagation of nervous power, but 

 not of electricity that if a piece of nerve be cut out and be 

 replaced by an electric conductor, electricity will be transmit- 

 ted when applied, but no nervous force excited by stimulus 

 above the section will pass to the parts below and that both 

 nerve and muscle are infinitely worse conductors of electricity 

 than copper or other metals. These facts are clearly opposed 

 to the present popular theory of the identity of nervous force 

 and electricity. 



More extended remarks upon our theory of the cause of 

 sensations would be out of place in a work of this kind ; yet as 

 the varied shapes and arrangement of the capillaries must be 

 demonstrated by means of the microscope, and as we have 

 seen no theory which attempts to explain the design of such 

 variations, an allusion to this seemed to be appropriate-. 



Hassall, in his Microscopic Anatomy, records an instance of 

 the capillary circulation being maintained for hours in a muti- 

 lated portion of a frog's tongue, which had been entirely sepa- 



