EMBRYOLOGIOAL METHODS. 335 



The dissecting-dish is then filled up with serum or liquid of 

 MULLER, or O'l per cent, solution of osmic acid, or KLEINEN- 

 BERG'S picro-sulphuric acid, or nitric acid, or acetate of 

 uranium solution. With a small scalpel a longitudinal in- 

 cision is made on the surface of the ovular eminence, not 

 passing deeper than the muscular layer ; the underlying 

 uterine mucosa is then gently dilacerated with two pairs of 

 small forceps, and the ovum set free in the liquid. 



From the moment the ova have become adherent to the 

 uterine mucosa they can no longer be extracted whole. The 

 embryo being always situated on the mesometrial surface, the 

 ovular eminence is opened by a crucial incision, and the strip 

 of mucosa to which the embryo remains adherent is fixed 

 with pins on the bottom of the dish. ED. v. BENEDEN (see 

 Arch, de BioL, v, fasc. iii, 1885, p. 378) has been able by 

 operating in this way in serum of Kronecker, and keeping 

 the whole at blood temperature, to observe the circulation 

 of the embryo for hours together. (If this be desired to be 

 done, the crucial incision should not be too extended, so as 

 to leave the terminal sinus intact.) 



RETTERER (C. R. Soc. de BioL, 1887, p. 99) advises that 

 for ova of the seventh day the segment of uterus containing 

 them be opened on the mesometrial surface, for at that date 

 no adhesion has yet been contracted with that side. By 

 running in liquid of Kleinenberg by means of a pipette 

 between the ovum and the free surface of the uterus, the 

 ovum may be got away in the shape of a closed vesicle. 



590. RABBIT ; Microscopic Preparations In order to make 

 permanent preparations of the different stages of fecundation 

 and segmentation, v. BENEDEN (Arch, de BioL, i, 1, 1880, p. 

 149) recommends the following process : The living ovum is 

 brought into a drop of 1 per cent, osmic acid on a slide, and 

 thence into solution of Miiller (or bichromate of ammonia or 

 solution of Kleinenberg). After an hour the liquid is 

 changed, and the whole is put into a moist chamber, where 

 it remains for two or three days. It is then treated with 

 glycerin of gradually increasing- strength, and at last mounted 

 in pure glycerin acidified with formic acid. Ova may be 

 stained after careful washing. 



In order to bring out the outlines of blastoderm cells the 



