294 CHAPTER XXV. 



can be opened with fine needles, and the blastoderm washed, 

 stained, or impregnated with gold, and mounted in glycerin 

 or balsam. 



For embryonic areas and more advanced embryos KOILIKER 

 recommends putting the ovum into 0*5 per cent, solution of 

 osmic acid until it has taken on a somewhat dark tint, which 

 happens in about an hour, and then treating it with successive 

 alcohols for several hours. If the ovum be adherent to the 

 uterine mucosa the portion of the membrane to which it is 

 fixed should be left, stretched out with pins, in O'l per cent, 

 solution of osmic acid for from four to six hours. The blasto- 

 dermic vesicle can then easily be removed, and further 

 treated as before. For sections KOLLIKEE fixes with osmic 

 acid. v. BENEDEN treats the ova for twenty-four hours with 

 1 per cent, solution of chromic acid, then washes well, and 

 brings them through successive alcohols. Chromic acid has 

 the advantage of hardening thoroughly the vesicle, and 

 maintaining at the same time the epiblast cells perfectly 

 adherent to the zona pellucida. v. BEN EDEN also recommends 

 the liquid of Kleinenberg. HENNEGUY writes that he fre- 

 quently employs it for embryonic areas and embryos of 

 various ages, always with excellent results. FoPs modifica- 

 tion of the liquid of Flemming, and Hanvier and Vignal's 

 osmic acid and alcohol mixture ( 36) also give excellent 

 results. For staining, HENNEGUY recommends borax-carmine, 

 or Delafield's haematoxylm for small embryos ; for large ones 

 he found that his acetic acid alum-carmine was the only 

 reagent that would give a good stain in the mass. 



For sections imbed in paraffin. 



ee also WEYSSE, Proc. A-iner. Acad. Arts, and Sci., 1894, 

 p. 285 (blastodermic vesicle of Sus fcrofa) ; SOBOTTA, Arch. 

 mik. Aiiat., xlv, 1895, p. 15 (ovum of the Mouse; fixation in 



FLEW MING'S weak mixture, sections stained with BENDA'S iron 



' 



haematoxylin), and Aimt. Hrfte, 1 Abth., viii, 1897sr 476 

 (Rabbit ; fixation with liquid of Flemming or pic 

 with 2 per cent, acetic acid) ; BONNET, Hid., ix, L)7, p. 426 

 (Dog; fixation in sublimate) ; SELK^KA, Stiid.EtJw. d. Thi<'re } 

 Wiesbaden, 1883, p. 5, and 1887, p. 107 (picrosulphuric acid 

 for the mouse, and picric acid with -j 1 ^ per cent, of chromic 

 acid for Didelphys) ; KEII:EL, Ncnj'h. Arl., ii, 1893, p. 1J 

 (Sus scrofa) ; NEUMAYEK, Fc'stxchr. /. Kitjffer, 1899, p. 458 



