xviii Journal of Comparative Neurology. 



Changes Due to Functional Activity in Nerve Cells.^ 



Dr. Hodges has performed numerous experiments upon several 

 vertebrates for the purpose of seeing what changes if any are pro- 

 duced in nerve cells as a result of activity. These experiments were 

 of two sorts ; in one case the ganglia were removed from animals that 

 had undergone normal fatigue ; in the other case fatigue was produced 

 artificially. In the first case a ganglion was removed from an animal 

 early in the morning and in the evenmg a corresponding ganglion was 

 removed from another specimen of the same animal. Both of these 

 ganglia were submitted to exactly the same hardening, staining, cutting 

 and mounting methods. For this purpose the author used spinal 

 ganglion and bram of English sparrow, pigeon, swallow, and the 

 brain of a honey bee. For producing the artificial fatigue use was 

 made of electricity. The ganglion was stimulated by a current from 

 a DuBois-Reymond coil. The circuit was broken once a minute by 

 means of clock work. At the end of the experiment the desired 

 ganglion and its mate on the opposite side were removed. From this 

 point on every effort was made to submit the ganglia to exactly the 

 same treatment. " In no instance were they separated from the time 

 they left the animal to the time when, placed side by side upon the 

 same slide, they appeared under the microscope for study. In every 

 case they were carried through the same reagents, in the same bottles 

 or dishes from the first fixing fluid to the solid paraffin. And further, 

 the two are cut at the same stroke of the microtome knife, fixed to 

 the slide together, stained together, and appear side by side in same 

 field of the microscope." For these experiments the author used: 

 spinal ganglia of dog, cat, and frog. 



The experiments thus conducted demonstrate, beyond a doubt, 

 that metabolic changes in nerve cells are as easily demonstrated as 

 similar changes in gland cells. 



Under the influence of fatigue, the nucleus decreases in size, 

 loses its reticulated appearance, and its cell wall becomes jagged and 

 irregular in outline. 



Under the influence of fatigue, in the spinal ganglia the cell pro- 

 toplasm shrinks slightly and becomes vacuolated; while in the cere- 

 brum and cerebellum, the cell protoplasm shrinks a great deal and 

 there is an enlargement of the pericellular lymph spaces. It was also 

 discovered that fatigue lessens the power of cell protoplasm to be 

 stained or to reduce osmic acid. 



1 Hodges, C. F. Study of changes due to Functional Activity in Nerve 

 Cells. Jour, of Morphology. Vol. VII, 1894, pp. 95-168; pi. VII-VIII. 



