No. 2.] CHANGES IN NERVE CELLS. 125 



is hence felt to be severe ; whereas if the electrodes are laid 

 full length upon the tongue, the stimulus can scarcely be felt 

 at all. The neglect of this fact at first has resulted in the use 

 of quite inadequate stimulation. 



Stimulation in this case was, however, severe. It was fre- 

 quently increased by sliding up the secondary coil, and was so 

 regulated as to produce the greatest possible amount of muscu- 

 lar contraction in the right fore leg without causing reflex con- 

 tractions in other parts of the body. Contractions in this leg 

 toward close of experiment were feeble but constant. Within 

 five minutes after the animal was bled, the muscles of this leg 

 had passed into rigor mortis, the muscles of all the other limbs 

 being normal and irritable. Pulse and respiration remained 

 normal the whole time. 



Aside from shrinkage of the nuclei, other important changes 

 occur. For the ist thoracic pair, hardened in osmic acid, the 

 nuclei are plump and round in the resting ganglion, and stain 

 lighter than the cell protoplasm. In the stimulated ganglion 

 they are irregular in outline and stain much darker than the 

 rest of the cell. This appearance is due not only to a darker 

 staining of the nucleus, but to a lighter staining of the cell. 

 Holding the osmic acid sections of resting and stimulated gan- 

 glia over a white surface, it is not difficult to see with the 

 unaided eye that the resting ganglion is stained darker than the 

 other. This indicates that a substance which reduces osmic 

 acid has been used up or changed, in the stimulated cell, into 

 something which does not reduce the acid ; while in the nucleus 

 more of something which reduces osmic acid has been produced 

 during stimulation. Examined microscopically, the lighter stain 

 is seen to be due to extreme vacuolation of the cell protoplasm. 

 This does not occur in the resting ganglion of the left side or 

 in the two thoracic ganglia used as control. The general appear- 

 ance is well shown in Figs, i and 2 of PI. VII ; although the 

 vacuolation of the cell protoplasm in Fig. 2 has not been well 

 copied from the original drawing. The protoplasm of all the 

 cells shows definite vacuolation to a greater or less extent.^ It 

 was also noticed independently by three ^ observers that the 



1 This appearance is better represented in Figs. 3 and 4, Amer. Jour. Psy., Vol. 

 II, p. 403. 



2 The three were Dr. H. H. Donaldson, Dr. Wm. H. Welch, and the author. 



