102 Journal of Comparative Neurology. 



have a bit of material protoplasm similar to that of other body 

 cells, and yet for a long time any structural change due to the 

 activity of the nerve cell eluded the keen vision of investigators. 

 It has been said that the secretion of a gland cell is of a ma- 

 terial character; that of a muscle cell, mechanical energy and we 

 might naturally expect to find in these tissues, changes demon- 

 strable by the microscope ; but the secretion of a nerve cell is 

 consciousness which is not exactly material, and its effect upon 

 the cell is too subtle to leave a trace. Hodge ^ in his fatigue 

 experiments extending over a period of four or five years, has 

 shown the fallacy of this view. His experiments dealing with 

 artificial and normal fatigue were performed in a most faithful 

 and conscientious manner on a wide range of forms with conclu- 

 sive results, the most of them having been confirmed by later 

 investigators. 



Fig. I. Fig. 2. Fig. 3. 



Figs. I, 2 and J, after Hodge. Only the cell bodies are shown. Fig. I, 

 represents the normal cell body with its large reticulated nucleus and the chro- 

 matin diffused throughout the cytoplasm. Fig. 2, shows the effects of fatigue, 

 the nucleus having become shrunken and irregular in outline, with a surround- 

 ing area devoid of chromatin. The peripheral portion of the cytoplasm is also 

 poor in chromatin. Fig 3, showing vacuolation of the cytoplasm as the ef- 

 fect of fatigue. 



For the artificial fatigue experiments the spinal ganglion 

 cells were chosen and the nerve connecting with the ganglion 

 was subjected to a weak electrical stimulation for a given length 

 of time. The spinal ganglion of the opposite side was removed 

 without stimulation and used as a control in the experiment, 

 the treatment of the two ganglia being identical after they were 

 removed from the body. In the fatigued cells he found slight 

 shrinkage in size, with vacuolation of the protoplasm. In the 

 nucleus there was a marked decrease in size, nearly 50% ; a 

 change from a smooth and round to a jagged, irregular out- 



> Jour. Morphology. Vol. VII. Pages 95—164. 1892. 



