262 EMBRYOLOGICAL METHODS. 



Muller, or O'l percent, solution of osmic acid, or Kleinenberg's 

 picro-sulphuric acid, or nitric acid, or acetate of uranium 

 solution. With a small scalpel a longitudinal incision 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 inucosa 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.) 



Preparation. 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 Muller (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 with Beale's 

 carmine or picro-carmine after removal from the osmic acid 

 and careful washing. 



In order to bring out the outlines of blastoderm cells, the 

 living ovum may be brought into one third per cent, solution 

 of nitrate of silver. After remaining there for half a minute 

 to two minutes, according to the age of the vesicle, it is 

 brought into pure water and exposed to the light. The pre- 

 parations thus obtained are instructive, but blacken rapidly 

 and cannot be permanently preserved. 



After the end of the third day the blastodermic vesicle can 

 be opened with fine needles, and the blastoderm washed, 



