552 NEUROGLIA AND SENSE ORGANS 



ten minutes in the fluid used for fixing, and then cut by the 

 freezing method. The sections are washed in distilled water and 

 stained for ten to thirty minutes, either at room temperature or 

 by careful gentle warming, with an ammoniacal silver carbonate 

 solution, prepared by adding to 10 c.c. or 10 per cent, silver 

 nitrate, first, 30 c.c. of 5 per cent, sodium carbonate, then aminonia, 

 drop by drop, until the precipitated silver carbonate is dissolved, 

 and, lastly, distilled water up to a total voluine of 150 c.c. The 

 sections are kept in the impregnating bath for from ten to thirty 

 minutes at room temperature, but they should nevertheless remain 

 almost colourless. 



They are then transferred directly without washing to 1 per 

 cent, formalin and kept moving about in this, either by blowing 

 on the surface or by moving them with a glass-rod until reduction 

 is complete. Finish as in Process I. 



The strength of the ammoniated silver carbonate solution 

 used in Process III may be varied. Hortega has more recently 

 used 5 c.c. of 10 per cent, silver nitrate and 20 c.c. of 5 per cent, 

 sodium carbonate, and after dissolving in ammonia made up 

 with distilled water to 45 c.c. (strong solution) or 100 c.c. (weak 

 solution). The strength of formalin may also be varied up to 

 10 per cent. 



The above refers to material fixed in Cajal's ammonium 

 bromide-formalin mixture ; if nervous tissues are fixed in 10 

 per cent, formalin and sections treated as in Process I, nerve- 

 cells and axis-cylinders become stained as by Bielschowsky's 

 method. If formol sections of non-nervous tissues are treated in 

 the same way, the reticular tissue becomes stained, 



1096. Other Silver Methods for Neuroglial Astrocytes. Globus 

 {Arch. Neurol, and Psychiat., xviii, 1927, p. 263) recommends the 

 following procedure for formalin fixed material before impregna- 

 tion by Cajal's method for neuroglia or Hortega's third process 

 for microglia (see § 1095). Frozen sections are thoroughly washed 

 in distilled water, placed in 10 per cent, ammonia for twenty- 

 four hours, washed again in distilled water, mordanted for two to 

 four hours in 10 per cent, hydrobromic acid and after a final 

 wash in weak ammonia water are stained by the selected technique. 



LuGARO {Arch. Suisse de Neurol, et de Psychiat., xxix, 1932, 

 p. 282) uses 15 per cent, formalin for fixing pieces of tissue 3 to 4 

 mm. thick before staining the protoplasinic neuroglia with varying 

 proportions of a mixture of silver bromide and silver iodide. 

 The pieces are stained in bulk for five to six days, allowing 10 c.c. 

 of solution for each piece, and after three hours in tlie solution 

 7 c.c. of 25 per cent, formalin are put in for each piece of tissue. 

 The stock solutions are : A, 9 per cent, sodium hyposulphite ; 



B, 2 per cent, silver bromide in 9 per cent, sodium hyposulphite ; 



C, 0-3 per cent, silver iodide in 9 per cent, hyposulphite. These 



