FINER STRUCTURE OF SYNAPSE 133 



twenty-four hours, rinsed with water, placed in 95 per cent alcohol for 

 twenty-four hours, and then placed in distilled water, till they sank to 

 the bottom and they were then put into the silver-bath for five to seven 

 days (in a 1 per cent silver solution for three to four days and in a 2 

 per cent solution for two to three days). For the reduction of the 

 impregnated silver a 2 per cent pyrogallic acid solution in 5 per cent 

 formol was used. The sections were cut at 5 to 10 yL. This preparation 

 offered excellent pictures of the synapses. and led to many interesting 

 findings, which will be described later. 



The Bielschowsky method of silver reduction also yielded nice pic- 

 tures of the intracellular neurofibrils and the synapse. The brains were 

 fixed in 10 per cent formol for twenty-four hours, rinsed with water, 

 dehydrated and cut in paraffin at 5 to 10 ix. The paraflSn was removed 

 with xylol and alcohol and the sections were thoroughly washed with 

 distilled water and placed in a 2 per cent silver solution for two to 

 three days. The sections were treated on the slide, following exactly 

 the directions of Bielschowsky. Some of the series were counter- 

 stained with eosin. 



For Heidenhain preparations, brains were fixed in Zenker's fluid or 

 in formol-Zenkr fluid. Some brains were put into the latter, after 

 being fixed first in 10 per cent formol for twelve to twenty-four hours. 

 The sections of 5 to 8 // were stained in the iron-hematoxylin of Hei- 

 denhain. This method gave not only a clear picture of the cell-body 

 and the synapse, but also a blue stain of the myelin sheaths that was 

 sometimes very advantageous. 



In addition to these preparations I prepared also a few series with 

 Held's neuroglia stain, Weigert's stain, and Mallory's stain. In all I 

 studied ninety-seven series of normal fish brains in the different methods, 

 classified as follows : 



(1) 5 series of Ameiurus nebulosus)^ Fixed in 95 per cent alcohol, and stained 

 5 series of Carassius auratus J with toluidin-blue and sometimes eosin. 



(2) 5 series of Ameiurus nebulosus\ Fixed in formol-Zenker fluid, stained with 

 5 series of Carassius auratus / thionin-eosin. 



(3) 5 series of Ameiurus nebulosusl ^^ . , 



,, . J ^ . ^ > Oajal preparation. 



11 series oi Carassius auratus J 



(4) 14 series of Ameiurus nebulosusl t j-^-. ,-, , 

 ' _ . - ^ . ^ } Levaditrs method. 



15 series of Carassius auratus j 



(5) 10 series of Ameiurus nebulosusl -d- i r , , 



„ . c r^ ■ X } Bielschowsky's stain. 



11 series of Carassius auratus j 



(6) 5 series of Ameiurus nebulosusl tt -j i • 



. . J. ^ . , > xleidenhain preparation. 



4 series of Carassius auratus j ^ 



(7) 2 series of Carassius auratus Held's neuroglia stain. 



(8) 2 series of Ameiurus nebulosus Mallory's stain. 



(9) 2 series of Ameiurus nebulosus Weigert's stain of myelin sheath. 



