FORMS OF PROTOPLASM. 33 



must be of a higher type than that of the 

 muscles, because it has to serve the higher 

 function of sensation ; that of the organs 

 of the senses must be of a higher type 

 than that of the nerves, because it has to 

 serve the higher functions of smell, hearing, 

 sight, etc. ; and that of the organ of the 

 mind the grey matter of the cerebral 

 hemispheres must be of a still higher, 

 indeed of the highest, type, because it has 

 to serve the very highest of life phenomena, 

 viz., those of conscious mind. These 

 differences depend, in all probability, on 

 differences in the number or arrangement 

 of the component molecules : they are, 

 however, much too subtle for our detection. 

 Nature works here with such infinitesimal 

 quantities and inconceivable arrangements 

 that we cannot even imagine them. 



The brain and the nerves are composed 

 of two kinds of substance, the white and 

 the grey : the white is made up of fibres, 

 the grey of cells. The surface of the brain 

 hemispheres is almost wholly grey matter 

 almost wholly cells and their connections. 



So much for the origin and nature of 

 the various forms of matter. This brings 

 us to the question of 



3 



