FIXATION AND HARDENING. 359 



cent, of osmium and per cent, of chromic acid in water, for 

 twenty-four to thirty-six hours, with subsequent hardening 

 for fourteen days in alcohol containing 2 per cent, of car- 

 bolic acid. He finds that the preservation of specimens so 

 treated is far superior to that of specimens hardened in pure 

 alcohol. 



SCHIEFFERDECKEE (Arch. f. mik. Anat., 1886, p. 305) used 

 either Miiller's solution, or chromic acid of | per cent., or a 

 mixture of 1 part of wood-vinegar (Acetum Pyrolignosum) 

 with 3 parts of distilled water, which he states gives particu- 

 larly instructive preparations without any serious alteration 

 of the elements. 



CUCCATI (Mem. E. Accad. Sci. 1st. di Bologna ; Zeit.f. wiss. 

 Mik., v, 1, 1888, p. 86) fixes large eyes (the lens and vitreous 

 body having been removed) for two days in a solution of 

 1 per cent, osmic acid . . .14 grms., 

 1 per cent, chromic acid . . . .25 



Acetic acid 1 drop, 



which should be renewed after the lapse of twenty-four 

 hours. 



See also DENNISSENKO (Arch. f. mik. Anat., 1881, p. 395). 



Dr. LINDSAY JOHNSON writes me that he gets the best results 

 by fixing for three minutes with a mixture of equal parts of 

 acetic acid and 2 per cent, osmic acid, injected into the 

 vitreous or the cavity of the eye. After that the eye is 

 washed in alcohol for a quarter of an hour, and put for two 

 hours into the mixture, 78 ; it is washed in running water, 

 and suspended in a large volume of 2*5 per cent, bichromate 

 of potash for two days, then passed gradually through suc- 

 cessive alcohols, beginning with 20 per cent., and ending with 

 absolute. 



CHIEVITZ (Arch.f. Anat. u. Phys., Anat. Abth., 1889, supp., 

 p. 139; Zeit.f. wiss. Mik., vi, 4, 1889, p. 511) uses nitric acid 

 of 2'5 per cent, strength. Entire heads of frogs may be fixed 

 in it for a couple of hours, washed out for a night in water, and 

 put up in alcohol. Bulbi of birds should be opened in the acid, 

 and the retina carefully exposed by removing the cornea, iris, 

 lens, and vitreous, or by separating the sclera and choroidea 

 from it. The duration of these operations affords a sufficient 

 fixation. 



ANGELUCCI (Moleschott's Untersuchungen, &c., xiv, 1890, 



