/-//•^, 



-culiar 



THE BEGINNINGS OF LIFE. 



35 



^ch 



source 



'^icalA., 



■'^^^^s thro. 



^'^'^^ % the 

 arc diss 



products of 

 muscle acts 



\ 



01 



;rtina a 



nical 



Portit 



f. 



energj 



not yieldii 



-indcrgoes me 

 i^'n functioni 



3. Turning now to the third mode of vital activity 

 to that which manifests itself in the display of nervous 

 phenomena — we shall find that these manifestations 

 are also closely dependent upon the integrity of certain 

 material structures, and that their appearance coincides 

 with an increase in the quantity of heat appreciable 

 in, or in the neighbourhood of these structures. 



The Nervous System is made up of nerve-cells and 

 nerve-fibres in various states of aggregation. The 

 nerve-cells are elements in which great molecular 

 changes are supposed to take place, attended by the 

 liberation of molecular motion, whilst the nerve-fibres 



jst as the p ^.x^^ f^j. ^^ m.o'sX. part, mere channels of communica- 



dual wear ant 



molecular 



luring its actii The matter of which the nervous system is com- 

 ly, by the nene,£ posed was originally almost uniform in structure and 

 ough not ffhollj, property ; but, little by little, developmental difiFeren- 

 3 exploding m tiations take place in the embryo, with which are 



associated correlated differences in function. As Mr. 



Herbert Spencer says, all direct and indirect evidence 

 he other han,"- c justify us in concluding that the nervous system con- 



ettro-physiologii 

 ort effected byj: 

 eater than the t 



d vigou 



r of the t 



ity of the nerr^. 



,.hich, in carta" 



nay in others t^^ 



n, 



and of the'': 



ir.m 



akei 



sists of one kind of matter under different forms and 

 conditions. In the grey tissue this matter exists in 

 masses containing corpuscles^ which are soft and have 

 granules dispersed through them, and which, besides 

 t^ being thus unstably composed, are placed so as to be 



M 



1 ex 



f he coi 



itrog**^ 



liable to disturbance in 



the greatest degree. 



In the 



r^ed the n'- - ,^. 

 , be transto"^ 



white tissue this matter is collected together in ex- 

 tremely slender threads that are denser, that are uniform 



D 2 



