50 FIXING AND HARDENING AGENTS. 



rendered extremely difficult. It causes a certain shrinkage of 

 chromatin. 



It is now almost always employed in the form of mixtures. For 

 these see 44, 45, 49, 76, as well as the mixtures given under " Picric 

 Acid" and "Formol." 



76. RABL (Zeit. wiss. Mikr., xi, 1894, p. 165) takes for embryos of 

 vertebrates, and also for other objects, 1 vol. of 1 per cent, platinum 

 chloride, 1 of saturated sublimate, and 2 of water. 



LENHOSSEK (Arch. mikr. Anat., li, 1898, p. 220) takes 20 parts of 

 1 per cent, platinum chloride, 20 of 5 per cent, sublimate, and 1 of 

 acetic acid. 



77. Palladium Chloride (SCHULZE, Arch. mik. Anat., iii, 1867, p. 

 477). Used by Schulze as a hardening agent in a 1 : 800 solution, 

 acidified with hydrochloric acid. 



CATTANEO has used it in solutions of 1 : 300, 1 : 600, or 1 : 800 strength, 

 for from one to two minutes, for Infusoria. 



FRENKEL (Anat. Ann., viii, 1893, p. 538) 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. 



78. Iridium Chloride (EISEN, Zeit. wiss. Mik., xiv, 1897, p. 195). 

 Solution of | or per cent., acidified with 1 per cent, of glacial acetic 

 acid. 



With the ovotestis of the snail, I have obtained about the worst 

 fixation I have ever seen, but with the testis of Triton much better 

 results. 



79. Osmium Chloride (EISEN, Journ. of Morph., xvii, 1900). Solution 

 of to ^ per cent. From specimens I have seen I should say it is 

 useless. 



80. Perchloride of Iron (FoL, Zeit. wiss. Zool., xxxviii, 1883, p. 491, 

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

 Tinct. Ferri Perchlor. B.P. 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 medullated nerve by PLATNER ( Zeit. wiss. 

 Mik., vi, 1889, p. 187). 



81. Iron Alum. STRONG (Journ. comp. Neur., xiii, 1903, p. 296) fixes 

 (and decalcifies) heads of young Acanthias in 9 parts of 5 per cent, 

 solution of iron alum with 1 of formol, for about two weeks. 



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

 Part II). GILSON (La Cellule, vi, 1890, p. 122) has used it 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 



DistiUed water , . . . . . 300 



Dry chloride of zinc .... 20 grins. 



