254 KIYOYASU MARUI 



many investigations by different authors (Golgi, Bethe, Held, 

 Bielschowsky, Auerbaeh, and many others). The lack of our 

 knowledge concerning the pathological manifestations in the 

 synapse and especially of experimental pathological data seems to 

 be dependent on the difficulty of technique on the one hand and 

 inaccessibility of adequate material on the other. In my recent 

 publication (24), I described more minute structures of the 

 synapse of the Mauthner cell of teleosts (bony fish). Per- 

 haps I have not made the structure of the synapse clear beyond 

 discussion; however, my results have been sufficiently definite 

 for me to attempt experimental work on the pathological con- 

 dition, especially in fatigue. Careful and thorough investigation 

 on this topic led me to very interesting results, which throw 

 light on the histological condition of the synapse in functional 

 activity, although it was forced far beyond the physiological 

 limit. In the present paper I will describe mainly the manifesta- 

 tions in the synapse as it was not my purpose to investigate the 

 neurocytological alterations of the Mauthner cell itself. But 

 wherever notable manifestations of the cell body appear, they 

 will be described as well as the findings of the synapse. To Dr. 

 Adolf Meyer I beg to express my high appreciation here for his 

 help and kind suggestions in this study. 



MATERIAL AND METHODS OF STUDY 



In the present investigation Ameiurus nebulosus was the ma- 

 terial of experimentation; Carassius auratus, which offered me 

 many interesting results in my previous work, proved to be un- 

 favorable material, owing to the fact that it is weak and often 

 dies before it comes to the utmost exhaustion. It was always at- 

 tempted in this experiment to work with strict control of the nor- 

 mal structure of the Mauthner cell as well as its synapse, and 

 care was always taken to avoid the formation of artefact as much 

 as possible. 



As a resting non-fatigued control, which was provided in each 

 experiment, I used a fish of about the same size which was kept 

 in a resting condition during the experiment of the other fish. 

 The body length of the fish used varied from 5 to 7 inches. 



