382 EMBRYOLOGY 



The following processes give good results as regards section- 

 cutting. 



Put the ova for a few minutes into 1 per cent, osmic acid ; 

 as soon as they have taken on a light brown colour bring them 

 into Miiller's solution. Open them therein with fine scissors — 

 the vitellus, which immediately coagulates on contact with air, 

 dissolves, on the contrary, in Miiller's solution — and the germ 

 and cortical layer can be extracted from the capsule of the ovum. 

 They should be left in clean Miiller's solution for a few days, 

 then washed with water for twenty-four hours, and brought 

 through successive alcohols. 



Another method (Henneguy) is as follows : The ova are 

 fixed in solution of Kleinenberg containing 10 per cent, of acetic 

 acid. After ten minutes they are opened in water containing 

 10 per cent, of acetic acid, which dissolves the vitellus. The 

 embryos are put for a few hours into pure solution of Kleinenberg, 

 and are then brought through alcohol of gradually increasing 

 strength. 



Child (quoted from Sumner, Mem. New York Acad. Sci., 

 ii, 1900, p. 78) fixes for about a minute in sublimate with 10 

 per cent, of acetic acid, and brings into formalin of 10 per cent.,' 

 which is said to give a good fixation of the embryo without the 

 yolk becoming hard. 



832. Kollmann's Fixative (Kollmann, Arch. Anat. Phijs., 1885, 

 p. 296). 



Bichromate of potash . . . . . 5 gm. 



Chromic acid . . . . . . 2 ,, 



Concentrated nitric acid . . . . 2 ,, 



Aq. dest. ....... 100 c.c. 



For ova of Teleostea. Fix for twelve hours, wash with water for 



twelve hours, then remove the chorion, and put the ova into 70 per cent. 



alcohol. , 



833. Rabl's Method, see § 834 ; for Kowalewsky's see Zeit. xviss. 

 ZooL, xliii, 1886, p. 434, or rhird Edition. 



834. Salmonidae. Henneguy's methods have been given, 

 § 831. 



KoPSCH {Arch. mik. Anat., li, 1897, p. 184), on the suggestion 

 of ViRCHOW, fixes embryos for five or ten minutes in a mixture 

 of 1 part of chromic acid to 50 of glacial acetic acid and 450 of 

 water, then removes into chromic acid of 1 : 500, and as soon 

 as may be removes the capsule and yolk under salt solution and 

 completes the hardening in the chromic acid or the saturated 

 sublimate solution. 



Similarly, Behrens {Anat. Hefte, x, 1898, p. 233). He opens 

 the ova in the salt solution from the aniipolar side, and frees the 

 embryo from the yolk that remains by blowing the latter away 

 with a fine-pointed glass tube. 



Similarly also Sobotta {ibid., 1902, p. 579). 



