THE NERVOUS TISSUE. 109 



composed of two substances, the one white, the other gray, 

 or cineritious. 



Under the microscope the white substance is found to 

 consist of fibres forming perfect cylinders, and varying in 

 diameter, having, according to Solly, an average diameter 

 of 1-2000 to 1-4000 of an inch. They consist of a trans- 

 parent neurilemma, containing a soft homogeneous sub- 

 stance, which on pressure assumes the knotted form, as 

 seen in 5, figure 13. This white substance constitutes the 

 whole of the nervous trunks and a large part of the central 

 masses. 



Its chemical constitution, by the analysis of Mr. John, 

 is Water 73, Albumen 9.9, White fatty matter 13.9, Bed 

 fatty matter 0.9, Osmazome 1, Earthy Phosphates 1.3. 



Besides these tubular fibres of the white nervous matter, 

 there are others belonging to the sympathetic nerves, 

 which are found to be only about half the diameter of 

 these fibres. They are of a grayish color and are called 

 organic fibres. 



The gray portion of nervous tissue, according to the 

 microscope, consists of spherical globules, containing a 

 nucleus with nucleoli, having a very fine filamentous cov- 

 ering and connected by processes to surrounding globules. 

 These globules are from 1-3000 to 1-1250 of an inch in 

 diameter. This gray matter forms the outer covering of the 

 Hemispheres of the brain, and is there called Cortical or 

 Cineritious. It exists in the interior of the spinal cord, and 

 composes the centre of the Ganglia. 



Its chemical constitution, according to the same chemist, 

 is Water 85, Albumen 7.5, White fatty matter 1, Eed fatty 

 matter 3.7, Osmazome 1.4, Earthy Phosphates 1.2. 



The gray matter is regarded as the source of nervous 

 power, and its collection at various points constitutes 

 the nervous Ganglia, which are regarded as so many 

 independent centres of nervous action; while the white 

 matter and its fibres are considered the conductors of the 

 nervous energy. 



The white and gray matter in varying proportions 



