1895.] MICROSCOPICAL JOURNAL. 303 



and amount of the nervous activity. Furthermore, as ani- 

 mals have two similar sides, one arm or leg may work and 

 the other remain at rest, and consequently corresponding- 

 sides of the nervous system may be active and at rest. 

 By means of electrical irritation one arm of a cat or 

 other animal was caused to move vigorously for a con- 

 siderable time, the other arm remaining at rest. Then 

 the two sides of the nervous system, that is the pairs of 

 nerves to the arms with their ganglia and a segment of 

 the myel (spinal cord), were removed and treated with 

 fixing agents, and carried through all the processes 

 necessary to get thin sections callable of accurate study 

 with the microscope. Finally, upon the same glass 

 slide are parts of the nervous system fatigued even to 

 exhaustion, and corresponding parts of the same animal 

 which has been at rest. Certainly if the nervous sub- 

 stance shows the result or processes of its action the 

 conditions are here perfect. Fatigued nerve cells are 

 side by side with those in a state of rest. The appear- 

 ances are clear and unmistakeable; the nucleus has mark- 

 edly decreased in size in the fatigued cells and possesses 

 a jagged irregular outline in place of the smooth rounded 

 form of the resting cells. The cell substance is shrunken 

 in size and possesses clear scattered spaces or a large 

 clear space around the nucleus. 



If the nervous substance was not fixed at once, but 

 remained in the living animal for twelve to twenty-four 

 hours in a state of repose, the signs of exhaustion dis- 

 appeared and the two sides appeared alike. By study- 

 ing preparations made after various periods of repose all 

 the stages of recovery from exhaustion could be followed. 



For possible cliange, in normal fatigue, sparrows, pig- 

 eons and swallows and also honey bees were used. For 

 example if two sparrows or two lioney bees as nearly 

 alike as possible were selected, the nervous system of one 



