426 NERVOUS SYSTEM SPECIAL METHODS. 



LIESEGANG (Kolloidchemie, Beihefte, iii, 1911, H. 7 ; Ztschr. wiss. Mikr., 

 xxviii, 1912, p. 369) makes sections of formol material by the freezing 

 process, and silvers them until yellow. He then adds to the silver bath 

 an equal volume of 50 per cent, solution of gum arabic and the same 

 amount of saturated solution of hydroquinone. After one or two 

 minutes the sections are brought into 10 per cent, solution of sodium 

 hyposulphite, washed and mounted. Results said to be the same as by 

 the usual process. 



ASCOLI (Boll. Soc. med. chir., Pavia, 1911, p. 177) recommends for 

 the sympathetic nervous system of Hirudinea the following : The 

 animals cut open at the back are stretched on a piece of cork and fixed 

 in a solution prepared by dissolving over a flame 5 gr. of pulverised 

 crystals of silver nitrate in 100 c.c. of 95 per cent, alcohol. After a few 

 minutes the animals may be detached from the cork and put back in 

 the same fixative for twenty-four to forty-eight hours in an incubating 

 stove. They are then transferred for another twenty-four to forty-eight 

 hours into a '10 per cent, watery solution of silver nitrate, to be kept 

 also in the incubator. After a quick wash they are reduced for five to 

 eight hours in Amidol- Hauff 0-5 gr., sodium sulphite cryst. 10 grms., 

 distilled water 100 c.c., and lastly passed into glycerin. Preparations 

 are made by teasing, the thinner ones being toned and counterstained 

 as usual. For mounting he prefers Apathy's syrup. 



HANSON (Anat. Anz., xlvi, 1914, p. 522) has the following for the 

 demonstration of non-medullated nerve fibres in cranial and peripheral 

 nerves : Fix in absolute alcohol containing 1 per cent, of strong 

 ammonia for forty.-eight hours ; rinse in distilled water, put in pyridine 

 for twenty -four hours, wash in many changes of distilled water for 

 twenty -four hours, place in 2 per cent, silver nitrate at 35 C. in the 

 dark for three days, rinse in water, and place for one day in a 4 per cent, 

 solution of pyrogallic acid in 5 per cent, formalin. 



As suggested by HABER and GUILD (Anat. Rec., vii, 1913, p. 253) the 

 results can be improved by a preliminary injection of 95 per cent, alcohol, 

 containing 1 per cent, of ammonia, through the arteries till tissues are 

 thoroughly saturated, after which they are dissected out and placed in a 

 similar arnmoniated alcohol solution for from two to three days. Huber 

 and Guild have found this method of use for the study of cranial nerves 

 of small animals and embryos, since the entire heads can, after fixation, 

 be decalcified by means of 7 per cent, nitric acid, brought through 

 80, 90, and 95 per cent, alcohols, each containing 1 percent, of ammonia, 

 and finally treated as above. 



840. BIELSCHOWSKY'S Methods. Introductory. It is well known 

 that, if ammonia be poured into a solution of silver nitrate, a pre- 

 cipitate is formed which is redissolved by the addition of some 

 more ammonia. If an alkaline solution of formaldehyde be slowly 

 added to this easily reducible di-ammoniacal silver nitrate 

 (N(NH 4 )AgH 2 N0 3 ), metallic silver is immediately precipitated and 

 deposited on the walls of the test tube. Both FAJERSTAJN (N enrol. 

 CentrbL, xx, 1901, p. 98) and BIELSCHOWSKY (ibid., xxi, 1902, p. 579) 



