CHAPTER XXXII. 431 



to the study of peripheral nerve endings. He fixes in 10 per cent, 

 formalin prepared with 60 per cent, alcohol, changes the fluid two 

 or three times, and then either leaves material therein until wanted 

 or keeps it in 70 to 80 per cent, alcohol. For staining, pieces are 

 brought into 10 to 12 per cent, formalin, and left in it until they are 

 quite free from alcohol. The rest as by Bielschowsky's method 

 for pieces, with or without pyridin treatment. Boeke finds that the 

 method succeeds also after other kinds of fixation. 



SCHLEMMER (Ztschf. wiss Mikr., xxvii, 1910, p. 22) makes the 

 ammoniacal silver nitrate-and-oxide bath by adding to any silver 

 nitrate solution, 40 per cent, caustic soda, drop by drop, until no more 

 precipitate is formed. He then washes the precipitate by repeated 

 decantation until the wash water no longer gives an alkaline reaction, 

 takes it up with the smallest possible quantity of ammonia, and filters 

 through glass wool. This concentrated solution keeps for many 

 days unaltered, and should be diluted ten times its volume before 

 using it. 



DEL Rio-HoRTEGA (Trab. Lab. Invest. BioL, Madrid, xiv, 1916, 

 p. 181) has made known a similar method used in those laboratories 

 for preparing the ammoniacal silver nitrate bath. Forty drops of 

 40 per cent, caustic soda are added to 30 c.c. of 10 per cent, silver 

 nitrate, and the precipitate washed ten to twelve times by means of 

 about a litre of distilled water. Fifty cubic centimetres of water are 

 then added to it, and ammonia, drop by drop, until the precipitate 

 is dissolved. The solution, brought finally to 150 c.c. and filtered 

 into a dark brown bottle, keeps well for many months. I find that 

 the ammoniacal silver bath thus prepared can be further diluted 

 with one, two, up to five times its volume of water, and usefully 

 employed for Bielschowsky's method for pieces, particularly for the 

 study of peripheral nerve endings. 



AGDUHR (Ztschr. wiss. Mikr., xxxiv, 1917, pp. 1-99), who has 

 exhaustively investigated almost all questions relating to the 

 results obtainable by Bielschowsky's method for pieces, has come 

 to the conclusion that material is best fixed in neutral or slightly 

 acid 20 per cent, formaldehyde (50 per cent, formalin). Pieces should 

 then be washed in distilled water for many days until the wash-water 

 is free from substances reducible by an ammoniacal silver nitrate 

 solution used as test. For the first silver bath he uses 3 per cent, 

 silver nitrate, and for the second a solution obtained by adding to 

 10 c.c. of 10 per cent, silver nitrate, first 20 drops of 25 per cent. 

 NaOH, then from 200 up to 600 c.c. of distilled water, and lastly 

 ammonia enough to dissolve the precipitate. For the reduction he 



