54 CROONIAN LECTURES 



the susceptibility of impression, and, from their 

 construction, giving them consequent reciprocal 

 action." (Hunter's Works, vol. iii., p. 115.) 



Again, he says : " The blood has as much the 

 materia vitop as the solids, which keeps up that 

 harmony between them." (P. 115.) 



Instead of a single vital fluid capable of 

 being an imponderable of all work, many dif- 

 ferent vital fluids, each capable of doing its own 

 work and no other, were assumed. The most 

 remarkable of all these was the nervous fluid. 



Glisson describes the vital fluid residing in 

 the nerves as resembling the spirituous part of 

 white of egg. Whether this was carbonate of 

 ammonia or sulphuretted hydrogen, must be 

 undetermined. 



Even Cuvier, in the introduction to the 

 Regne Animal, p. 30, says : " There is great 

 probability that it is by an imponderable fluid 

 that the nerve acts upon the fibre ; and that 

 this nervous fluid is drawn from the blood and 

 secreted by the medullary matter." 



Johannes Mliller taught that the nervous 

 agent differed entirely from electricity or light, 

 but was either an imponderable matter, or the 

 undulations of a fluid capable, like electricity 



