EFFECT OF OVER-ACTIVITY ON SYNAPSE 255 



The experiment consisted in forced activity of the fish, carried 

 to the most advanced stage of fatigue; the experimental fish was 

 placed in a jar 7.5 inches in diameter and about 8.5 inches in 

 depth and then the water in the jar was continually stirred by 

 running water, which came with high pressure from a faucet. The 

 fish swims in the stirred water, trying all the time to hold its 

 equilibrium. According to Bartelmez (3), the Mauthner cell 

 participates in the equilibratory reflex; so it was supposed that 

 in this experiment the Mauthner cell would be forced into con- 

 tinuous activity. The duration of the experiment varied re- 

 markably in each fish (from 24 to 98 hours). At first the fish 

 swims actively and is able to hold its equilibrium very well, but 

 gradually it gets tired and in the final stage of the experiment it 

 is deprived of the ability of balancing, so that it is moved pas- 

 sively tumbling around in the stirring water. By this time if we 

 stop the running water for a moment, the fish would lie on its back 

 or on one side, showing no attempt to maintain its upright pos- 

 ture. As the sign of utmost exhaustion, I chose a test, which con- 

 sisted in holding the fish upside down by its tail in the water as 

 well as in the air. In the most advanced stage of exhaustion the 

 fish did not flap at all even in this test. 



The fish was then decapitated and bled, the brain was quickly 

 but carefully dissected out and fixed in 10 per cent formalin, for- 

 mol-Zenker fluid, and alcohol (95 per cent), respectively. The 

 resting control fish was killed at the same time and the brain was 

 manipulated in .quite the same way as the fatigued brain. It 

 must be emphasized also that the material was always fixed fresh 

 and that material from fish which died was not examined. 



From the material thus obtained, the following preparations 

 were made with the same technique as was described in my recent 

 publication : 



1. Thionin-eosin preparation (1 series each of normal and 

 fatigued brains) . 



2. Toluidin-blue preparation (5 series each of normal and 

 fatigued brains). 



3. Heidenhain preparation (6 series each of normal and 

 fatigued brains). 



