FIXING AND HARDENING AGENTS. 61 



78. Palladium. Chloride (F. E. SCHULTZE, Arch. mik. Anat., Hi, 1867, 

 p. 477). This reagent was recommended by Schultze as a hardening 

 agent, partly as giving to tissues a better consistency than chromic acid or 

 Miiller's solution, and partly on account of a special faculty for penetrating 

 organs rich in connective tissue that he attributed to it. It is an impreg- 

 nation reagent, staining certain elements of tissues in various tones of 

 brown. For the somewhat lengthy details of the manner of employing it, 

 the reader is referred to the paper quoted. 



CATTANEO recommends it, used in solutions of 1'300, 1'GOO, or 1'SOo 

 strength, for from one to two minutes, as being the best of fixatives for 

 Infusoria. 



This salt is found in commerce in the solid state. To dissolve it, take 10 

 grammes of the salt, one litre of water, and four to six drops of hydrochloric 

 acid. Solution will be effected in twenty-four hours. 



FRENKEL (Anat. Anz., viii, 1893, p. 538; Zeit.f. wiss. Mik., x, 2, 1893, 

 p. 243) recommends for connective tissue a mixture of 15 parts 1 per cent, 

 palladium chloride, 5 parts 2 per cent osmic acid, and a few drops of acetic 

 acid. 



79. Iridium Chloride (EiSEN, Zeit.f. wiss. Mik., xiv, 2, 1897, p. 195). 

 Solution of one half or one fifth per cent., acidified with 1 per cent, of 

 glacial acetic acid. 



My specimens show about the worst fixation I have ever seen. It simply 

 does not fix at all. 



80. Perchloride of Iron (FoL, Zeit. f. ivixs. Zool., Bd. xxxviii, 1883, 

 p 491; and Lehrb. d. vergl. mik. Anat., p. 102). Fol recommends 1 vol. 

 of Tinct. Ferri Perchlor. P. B. diluted with 5 to 10 vols. of 70 per cent, 

 alcohol. 



The tincture diluted with 3 to 4 vols. of either alcohol or water has been 

 recommended for fixing niedullated nerve by PLATNER (Zeit.f. iviss. Mil; . 

 vi, 2, 1889, p. 187). 



81. Chloride of Zinc is sometimes used for hardening brain (see 

 Part II). GILSOX (La Cellule, vi, 1, 1890, p. 122) has used it with good 

 results as a fixative for the silk-glands of Lepidoptera, as follows : 



Glacial acetic acid ..... 5 c.c. 

 Nitric acid of 46 (or 80 per cent, nearly) 5 ,, 



Alcohol of 80 per cent. . . 100 



Distilled water 300 ,, 



Dry chloride of zinc . 20 grammes. 



81a. Fluorides (MARPMANN), see Zeit. f. angeiv. Mik., v, 1899, p. 33, 

 or Journ. Roy. Mic. Hoc., 1899, p. 456. 



