2 Edward F. M alone. 



topograpliical regions are observed, the cells being stained instead of 

 the fiber;;. When the cell character is noted it is done usually in a 

 superficial manner and principally for the purpose of orientation, and 

 with no purpose of bringing the cell character into relation with a 

 definite function. 



The same lack of attention to the cell tyjie is apparent even in the 

 work of the relatively few investigators who employ the experimental 

 methods of Xissl or von Gudden. The following instance is a good 

 illustration of the value of carefully noting the cell character of various 

 cell groups. In his excellent study of the dorsal (sympathetic) nucleus 

 of the vagus nerve Molhant had shown that all the cells of this cell 

 column give origin to all of the vagus fibers which supply smooth 

 muscle and heart muscle, and that certain portions of this cell column 

 supply smooth muscle while a definite portion supplies heart muscle, 

 but he did not attempt to show that a definite type of cell was involved 

 in the innervation of each of these two types of muscle ; after studying 

 the vagus sympathetic nucleus I was able to show that the portions of 

 the nucleus which supply smooth muscle and heart muscle may be 

 readily distinguished by the fact that they are composed of cells of 

 difi'erent types, and that just as heart muscle is histologically inter- 

 mediate between smooth muscle and striated muscle, just so the cells 

 of the vagiis sympathetic nucleus which supply heart muscle are of a 

 histological character intermediate between that of the cells which 

 supply smooth muscle and striated muscle. Such an observation of the 

 relation of cell type to cell function enables us to locate accurately a 

 functional center even though its cells be mixed with those having a 

 different function, and homologous centers may be recognized in 

 different animal fonns; at the same time it emphasizes the necessity 

 of carefully noting the cell character of each cell group, so that even if 

 the function is imknown the presence of a definite cell type will offer a 

 problem for future experimental work, and in the meanwhile preclude 

 the possibility of confusing this cell group with surrounding cells. 

 These differences in cell type are of course most definite in the higher 

 mammals and especially in man, where the various cell groups are 

 highly specialized. 



The foregoing consideration of the failure of workers on the anatomy 

 of the mammalian brain to attach sufficient importance to the different 

 types of cells explains why such characteristic cell groups as the basal 

 optic ganglion and the nuclei tuberis have not been clearly separated 



