36 



PHYSIOLOGY AND MORPHOLOGY OF ANIMALS 



fibrous matter (Fig. 20). The white fibrous matter seems 

 to be made up wholly of slender fibers which come from 

 the cells of the gray matter. We may imagine these 



fibers coming from the sur- 

 face gray-matter cells, con- 

 verging to form the white 

 matter of the brain, and then 

 passing out of the skull to 

 form the spinal cord, to be 

 distributed everywhere. Or, 

 conversely, we may conceive 

 fibers of the spinal cord com- 

 ing into the brain and diverg- 

 ing to end in the cells of the 

 surface gray matter. Then, 

 last of all, these gray-matter 

 cells send out each of them 

 fibers which connect with 

 those of other gray-matter 

 cells. Now it is probable that 

 such a cell with all its fibers, 

 Fig. 2a— Vertical section of a both those connecting with 



convolution of the brain, show- other ceUs and the long fiber 

 ing the cells of the gray gran- ° 



ular matter (g g ) giving out (axis cylinder) connecting 



fibers which go to form the . . . . . , , 



white fibrous matter (w / ) be- with other parts ot the body, 

 low. After Luys. together constitute one indi- 



vidual cell. Such an individual element of nerve matter 

 is called a neurone. On this view the brain, and indeed 

 the whole nerve system, may be regarded as naught else 

 than a collection of neurones intricately connected. The 

 fibers connecting neurones are not simple, but branching 

 (dendrites), and the connection is not continuous, but 

 by contact. They do not unite, but only touch fingers 

 or interlace dendrites (Fig. 21).* 



* Professor Turner, British Association Address, 1897. Mathi- 

 as-Duval, Rev. Sci., vol. ix, p. 321, 1898. 



