268 niYsioLOGY of muscles a>d nerves. 



(3) They can receive an excitement transmitted to 

 them and transmute it into conscious sensation. 



(4) They are able to cause the suppression (retar- 

 dation) of an existing excitement, 



4. From the above it must not be supposed that all 

 ganglion-cells possess all these qualities. On the con- 

 trary, it is to be supposed that each nerve-cell per- 

 forms but one of these functions, and even that there 

 are more minute differences in them, so that, for in- 

 stance, the nerve-cells which accomplish sensation are 

 of various kinds, each of which accomplishes but one 

 distinct kind of sensation. This is no mere hypo- 

 thesis, for there are established facts which confirm 

 the view. Conscious sensations occur only in the brain, 

 and the various parts of the brain may be separately 

 removed or disabled, in which case individual forms 

 of sensation fail, while others remain undisturbed. 

 If the whole brain is removed, the nerve-cells of the 

 dorsal marrow suffice fully to accomplish the pheno- 

 mena of the transference of excitement from one nerve- 

 fibre to another. Again, there are certain regions of 

 the brain which separately are able to give rise to inde- 

 pendent excitement in themselves ; and certain accumu- 

 lations of nerve-cells which lie outside the actual central 

 nervous organs have the same power. The forms which 

 nerve-cells assume being very varied, it often happens 

 that the cells of certain regions, where only certain capa- 

 bilities can be shown, are alike in form, and differ in this 

 respect from the cells of other regions, where the capa- 

 bilities are different. As yet^ however, it has not been 

 found possible to distinguish differences in form suffi- 

 ciently characteristic, and relations between the form and 

 the function of nerve-cells sufficiently characteristic to 



