132 KIYOYASU MARUI 



he further analyzed the elements of the pecuUar synapse of this 

 giant cell. Lately I had the opportunity to do some experimental 

 pathological study on this wonderful cell and its synapse, the 

 results of which will appear soon. Careful and thorough investi- 

 gations led me, however, to many interesting conclusions in re- 

 gard to the structure of the synapse and the mode of conjunction 

 of nerve cells; I will therefore describe these results in the present 

 paper with special considerations of the condition in higher ver- 

 tebrates. I beg to express here my gratitude to Dr. Adolf 

 Meyer for his constant help and frequent advice in this work. 



MATERIAL AND METHODS OF STUDY 



The present work is based upon the investigation of serial sections of 

 brains of adult Ameiurus nebulosus and Carassius auratus. The fish 

 were decapitated, bled, and the brains were dissected out carefully but 

 quickly, and placed promptly in different fixatives; the methods of 

 preparation used are as follows: 



At first I mention the toluidin-blue preparation, in which brains 

 were fixed in 95 per cent alcohol for twelve to twenty-four hours. Par- 

 affin sections 8 to 10 ^i thick were stained in 1 per cent warm aqueous 

 solution of toluidin blue, differentiated in alcohol and sometimes coun- 

 terstained with eosin. 



Other brains were fixed in formol-Zenker fluid twelve to twenty-four 

 hours, cut at 8 )Li in paraffin, stained in a saturated solution of tliionin 

 in a 1 per cent aqueous solution of carbolic acid and counterstained 

 with eosin after differentiation in alcohol. 



For Cajal preparations brains were placed twelve to twenty-four 

 hours in alkaline alcohol (96 per cent alcohol with 1 per cent ammonium 

 hydroxid). The fixed brains were then rinsed with 95 per cent alcohol, 

 placed in distilled water till they sank to the bottom of the container 

 and then they were placed in the silver-bath of 37° to 40 °C. for ten 

 to fourteen days, according to the size of the pieces. As silver-bath I 

 used a 1 per cent silver-nitrate solution for the first seven to ten days, 

 with one change, and then a 2 per cent solution with one change, in 

 which the pieces were kept three to four days. They were then rinsed 

 with distilled water and developed twelve to twenty-four hours in 1 

 per cent pyrogallic acid solution in 5 per cent formalin, again rinsed 

 with water, dehydrated and cut in paraffin 5 to 10 ju thick. This al- 

 ways gave good results; in my experience the Mauthner cells are very 

 apt to show shrinkage space after fixing in acetic alcohol for a short 

 time (Bartelmez) (4), which is unfavorable for the study of the synapse. 



I next applied the Levaditi method for spirochaeta pallida to the 

 fish brain. The brains were fixed in 10 per cent formol twelve to 



