STRUCTURE OF NERVE-CELLS. 129 



Fig. 7. — A large branched nerve-cell, or " mind-cell," from the brain of 

 an Electric Fish (Torpedo) ; 600 times the natural size. The large, bright, 

 glubular kernel (nucleus) lies in the centre of the cell ; this nucleus contains 

 a nucleolus, and in that, again, there is a nucleolinus. The protoplasm of 

 the cell has separated into innnmerable fine threads (or fibrillae), which are 

 embedded in the inter-cellular substance, and which pass out into the 

 branched processes of the cell. An unbranched process (a) passes over 

 into a nerve vessel. (After Max Schultze.) 



cell, an elementary organ of mental activity. Correspond- 

 ingly, it has an extremely complex minute structure. Innu- 

 merable filaments of exceeding fineness, wliich may be com- 

 pared to the numerous electric wires of a great central 

 telegraph station, traverse, crossing each other again and 

 again, the finely granulated protoplasm of the nerve-cell 

 and pass into branched processes, which proceed from this | 



mind-cell, and connect it with other nerve-cells and nerve- | 



fibres (a, h). It is scarcely possible to trace, even approxi- \ 



mately, the tangled paths of these filaments in the fine 

 substance of the protoplasmic body. 



We thus have before us a highly complex apparatus, ; 



the more minute structure of which we have hardly begun 'j 



to know, even with the help of our strongest microscope, j 



and the si^^nificance of which we rather p'uess than know. I 



Its complex mechanism is capable of the most intricate i 



psychical functions. But even this elementary organ of 

 mental activity, of which there are thousands in our brain, 

 is only a single cell. Our whole intellectual life is but the ] 



sum of the results of the activity of all such nerve-cells or i 



mind-cells. In the centre of each cell lies a large trans- ; 



parent ball, which encloses a smaller dark body. This is 

 the nucleus which contains the nucleolus. Here, as every- | 



where, the nucleus determines the individuality of the 

 cell, and shows that the entire formation, notwithstanding 



