732 THE POPULAR SCIENCE MONTHLY. 



These proceedings offer a considerable number of facts not readily 

 classifiable under any theory now at hand. 



There is present and urgent need for a clear statement of the case 

 respecting nerve-matter and consciousness. There is equally urgent 

 need that this statement should be reasoned upon according to the 

 fundamental working of reason — viz., the detection of difference and 

 similarity. It is the proper reward of modern science to have taught 

 that reasoning is the procedure from the known to the unknown by 

 the pathway of resemblance. This resemblance must be experiment- 

 ally determined and experimentally verified. Dr. Maudsley says, most 

 truly, in his last edition of the " Physiology and Pathology of the 

 Mind " : " It will not advance knowledge to identify phenomena of a 

 different kind by giving them the same name ; on the contrary, the 

 progress of knowledge lies in following the specializations of develop- 

 ment, and in defining differences by a precise use of terms." The 

 characteristic phenomena of nerve-matter and the characteristic phe- 

 nomena of consciousness should be stated and compared : if these phe- 

 nomena prove different, they should be described, in the light of that 

 difference, and all conclusion as to their origin should be drawn ac- 

 cording to that difference. Our first inquiry, then, is concerning the 

 nervous system, as to its parts and functions. 



The histological elements of the nervous system are two, the fiber 

 and the cell. The fiber appears under two forms, the medullated and 

 non-medullated. The medullated fiber consists of a central thread or 

 axial band, then a soft substance called the medulla, and, inclosing 

 these, a tubular sheath. The axial band is the essential anatomical 

 element of the fiber. It is an albuminoid substance— that is to say, it 

 is highly unstable in character and complex in structure. The medul- 

 lary substance is transparent, homogeneous, and strongly refracting, 

 like oil ; it consists chiefly of lecithin and cerebrin. The sheath is a 

 lime-substance. The differences in chemical composition between this 

 axial band and its marrow-like inclosure were shown by Lister and 

 Turner in 1859. The band becomes red by a solution of carmine, 

 while the marrow substance is unchanged, and in turn this substance 

 becomes opaque and brown under chromic acid, while the band re- 

 mains unaltered. 



The second element of nerve-matter is the cell. This, in its fully 

 developed condition, is of irregular shape, with strongly refracting 

 granular contents and a distinct nucleus and nucleolus. Many of the 

 cells have one or more prolongations, and are accordingly classed as 

 unipolar, bipolar, or multipolar. One at least of the processes of a 

 multipolar cell is continuous with a fiber and is called the axial-cylin- 

 der process. In the cells and in the intercellular substance of central 

 nerve-organs, albuminoid stuff is closely mingled with the other com- 

 ponent parts of nerve-matter. 



The proportion of solids to water is but twelve per cent in the 



