NERVUS TERMINALIS IN AMIA 51 



after each use for clearing, in order to evaporate the alcohol 

 introduced. Dehydration was accomplished by passing the 

 pieces quickly through the lower grades of alcohol, which have a 

 tendency to dissolve the silver precipitate, and was made com- 

 plete by two changes of 95 per cent, and of alsolute alcohol at 

 intervals of about two hours. Pieces were finally left in cedar 

 oil for twelve to twenty-four hours. From the cedar oil the 

 pieces were transferred to melted paraffin which was changed 

 three times at intervals of three or four hours in order to have 

 the blocks free of cedar oil. By lowering an electric light bulb 

 over the block while cutting in cool weather, sections more than 

 50 micra thick can be cut in ribbons with ease. 



Series of adult brains by the Weigert method were cut in three 

 different planes and a transverse series of the head of a young 

 Amia 100 mm. in total length was made. The iron hematoxylin 

 method recommended by Houser ('01) gave better results than 

 the Weigert method in the forebrain where there is little medul- 

 lation. Bielschowsky's formalin-ammonia-silver method was 

 tried with some success, but by far the best results were given 

 by the Cajal ('05) treatment for the anterior part of the brain 

 and for certain fibers in the olfactory capsules. For showing 

 axones by the Cajal method, the best preparations were made 

 after fixation in 95 per cent alcohol. In some cases a small 

 amount of ammonia was added until there was a slight reaction 

 to litmus paper. Material thus fixed may be kept in 80 per cent 

 alcohol until it is convenient to employ the silver bath. Small 

 pieces were kept warm in silver nitrate of about 2 per cent, for 

 from three to five days. The same precautions were taken as 

 for Golgi preparations to avoid xylol and the prolonged use of 

 low grades of alcohol in embedding. Paton's ('07) modification 

 of Bielschowsky's method was tried on embryos and young of 

 Amia. It showed neurofibrils in none but the larger elements 

 of the brain in the later stages after hatching. 



Nissl preparations were made of the brains of adults to show 

 regional differentiation and to demonstrate the characters of the 

 cells of the nervus terminalis. Material fixed in Graf's chrom- 

 oxalic mixture cited by Houser ('01) gave better results than 



