CHAPTER XXXI. 405 



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

 the freezing method. 



NELIS (Bull. Ac. 8c. Belg., 1899-1900) fixes spinal ganglia for twenty- 

 four hours in a solution of 20 grms. of copper sulphate and corrosive 

 sublimate to saturation in a litre of 7 per cent, formol with 5 c.c. of 

 acetic acid. 



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, celloidiu for two to three days, and 

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

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

 bichromate mixtures that equals it. All sublimate mixtures fix the 

 nuclei well, but vacuolise the cytoplasm. 



See further particulars on this subject in the original papers of 

 TRZEBINSKI, Virchow's Arch., cvii, 1887, p. 1 ; DIOMIDOFF, ibid., p. 499 ; 

 FISH, The Wilder Quarter-Century Book, 1893, p. 335 ; DONALDSON, 

 Journ. Morphol., ix, 1894, p. 123 ; MARINA, Neural. Centrbl., xvi, 1897, 

 p. 166 ; TIMOFEEW, Intern. Monatschr. Anat., xv, 1898, p. 259. 



814. Nervous Centres of Reptiles, Fishes and Amphibia. MASON 



(Central Nervous System of Certain Reptiles, etc. ; WHITMAN'S Methods, 

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

 cent, bichromate, changed once a fortnight until the hardening is 

 sufficient (six to ten weeks). 



BURCKHARDT (Das Gentralnervensystem von Protopterus, Berlin, 1892 ; 

 Ztschr. wiss. MiTcr., ix, 1893, p. 347) recommends a liquid composed of 

 300 parts of 1 per cent, chromic acid, 10 parts of 2 per cent, osrnic 

 acid, and 10 parts of concentrated nitric acid, in which brains of 

 Protopterus are hardened in twenty-four to forty-eight hours. 



FISH (Journ. of Morphol., x, 1895, p. 234) employed for Desmog- 

 nathus a mixture of 100 c.c. of 50 per cent, alcohol, 5 c.c. of glacial 

 acetic acid, 5 grms. of corrosive sublimate, and 1 grm. of picric acid, fixing 

 for twelve to twenty-four hours, and passing through the usual alcohols. 



STRONG (Journ. comp. Neurol., xiii, 1903, p. 296) fixes (and decalcifies 

 at the same time) the heads of young Acanthias in a mixture of 9 parts 

 of 5 per cent, iron alum and 1 part of formol, for about two weeks, 

 makes paraffin sections, stains with hsematoxylin, and differentiates in 

 1 or 2 per cent, iron alum. 



JOHNSTON (Morphol. Jahrb., xxxiv, 1905, p. 150) recommends for 

 nerves of Petromyzon to make paraffin section from Zenker material, 

 and stain them with a mixture of saturated solution of nigrosin, 

 saturated solution of picric acid, and 1 per cent, acid fuchsin, in water 

 mixed in proportions arrived at by trial. 



Sections. 



815. Imbedding is by no means always necessary, and is objected 

 to in some cases. Indeed sections can be obtained from any part 



