NERVOUS SYSTEM— GENERAL METHODS 461 



Nitric acid has been and still is employed in strengths of 10 to 12 per 

 cent. 



Ten per cent, neidral acetate of lead affords, according to Kotlarewski 

 (Ztschr. wiss. Mikr., iv, 1887, p. 387), an excellent preservation of 

 ganglion cells. 



Corrosive sublimate solutions either alone or mixed with other reagents 

 (see Chapter V), have been very often used for cytological studies. 



Similarly acetic alcohol. 



Mann {Ztschr. tviss. Mikr., xi, 1894, p. 480) recommends for cell 

 studies the following fluids : — 



(1) Heidenhain's saturated solution of corrosive sublimate in physio- 

 logical salt solution ; (2) saturated watery solution of corrosive sub- 

 limate with 1 drop of nitric acid to every cubic centimetre of the 

 sublimate solution ; (3) Heidenhain's sublimate solution with 1 grm. 

 of picric acid and 1 of tannin ; (4) equal parts of 1 per cent, osmic acid 

 and Heidenhain's sublimate solution. 



Mann (op. cit.) for cell studies, puts small pieces for twenty-four hours 

 into a solution of 5 parts of potassium iodide and 25 of iodine in 100 

 parts of water, and then into 70 per cent, alcohol. 



Olmacher (§ 70) recommends his mixture. Kodis (Arch. mikr. 

 Anat., lix, 1902, p. 212) fixes tissues in a saturated solution of cyanide 

 of mercury, brings them into 10 per cent, formol, and makes sections by 

 the freezing method. 



Nelis (Bull. Ac. R. Belg. cl. d. sc, xxxvii, 1899, p. 102) fixes ganglia 

 for twenty-four hours in Gilson's fluid. 



King {Anat. Rec, iv, 1910, p. 213), after trying over twenty-five 

 methods on brains of rats, concludes that the best is Ohlmacher's. 

 The brain should be put into it for two to three hours, then for one into 

 85 per cent, alcohol, then into 70 per cent, with iodine for at least 

 twenty-four hours, then passed through alcohols of ascending strength 

 and alcohol-ether into 2 per cent, celloidin for two to three days, and 

 through chloroform and benzol into paraffin. In her opinion, Bouin's 

 is the best of the formol liquids ; Tellyesniczky's is the only one of the 

 bichromate mixtures that equals it. All sublimate mixtures fix the 

 nuclei well, but vacuolise the cytoplasm. 



986. Marina's Method {Neurol. Centralb., xvi, 1897, p. 166) has the 

 great advantage of allowing the subsequent carrying out of a great 

 variety of staining methods. The material should be fixed in a mixture 

 of 100 c.c. of 90 per cent, alcohol, 5 c.c. of formalin, and 010 grm. of 

 chromic acid. On the following day the pieces are reduced in size and 

 placed in some freshly-prepared fixing fluid for another two to five 

 days. They are then gummed to wooden cubes, and these are preserved 

 in 90 per cent, alcohol, to which about 1 per cent, of chromic acid may 

 be added. The sections can be stained by Nissl's soap-methylen blue 

 method § 1001) or with thionin, or by a modification of Held's method 

 for neurosomes (§ 1005). If they are transferred into chromogen they 

 can be used for staining neuroglia fibres by Weigert's method (§ 1083) ; 

 if mordanted as suggested, by Vassale (§ 1056), or in 3 per cent, potas- 

 sium bichromate to which a few drops of ammonia have been added, 

 they can be employed for staining medullated nerve fibres. 



See further particulars on this subject in the original papers of 

 Trzebinski, Virchoxv's Arch., cvii, 1887, p. 1 ; Diomidoff, ibid., p. 499 ; 

 Fish, The Wilder Quarter-Ceri urij Book, 1893, p. 335; Donai-dson, 

 Journ. Morphol., ix, 1894, p. 123 ; Timofeew, Intern. Monatschr. Anat., 

 XV, 1929, p. 259. 



987. Nervous System of Reptiles, Amphibia and Fishes. Mason 

 {Central Nervous Si/stem of Certain Reptiles, etc. ; Whitman's Methods, 

 p. 196) recommends iodised alcohol, six to twelve hours ; then 3 per 



