264 H. M. KINGERY 



MATERIAL AND METHODS 



The material on which this study is based consists of a rather 

 complete series, serially sectioned, of ovaries of white mice 

 ranging from embryos of 10 mm. length to adults — in all nearly 

 300 ovaries. From birth to two days afterwards, the. ovaries 

 were fixed at intervals of two to three hours; from two to forty 

 days, at intervals of one day; and from forty to sixty days, at 

 intervals of five days. A number of ovaries from adult mice, 

 pregnant and not pregnant, were also fixed. The series of embry- 

 onic and foetal ovaries ranges from those of embryos 10 mm. in 

 length, at intervals of one millimeter, to foetuses 25 mm. long, 

 or practically full term. These embryos, according to Kirk- 

 ham's table ('16 a) range from about fourteen to twenty or twenty 

 one days post coitum. 



For fixation, Hermann's, Flemming's, Carnoy's (6-3-1, with 

 and without the addition of mercuric chloride), picro-aceto- 

 formol (Bouin's), and sublimate-acetic were used, each ovary 

 of a mouse being treated in a different manner. It was found 

 that Hermann's and Flemming's fluids preserved the nuclear 

 structure excellently in the interior of the younger ovaries, but 

 that the outer two or three layers of cells were over-fixed, pre- 

 senting the glassy, homogeneous appearance with lack of detail 

 characteristic of cells over-fixed with osmic acid. Carnoy's 

 fluids gave excellent preservation of the nuclei, but in a number 

 of cases the sections, when stained with iron hematoxylin, 

 showed a solid black band or border, one to three cells deep 

 around the ovaries, completely obscuring detail. Picro-aceto- 

 formol was the most useful and successful fixing fluid for pre- 

 serving the outer layers of cells — particularly the germinal 

 epithelium. I might add that where there was any tissue in 

 contact with the ovaries (a bit of the peritoneal wall was some- 

 times snipped off with the smaller ovaries) 'or where the peri- 

 ovarian capsule was thicker than usual, due to its penetration 

 by the oviduct, Flemming's fluid preserved the outer cells very 

 well, the extraneous tissue becoming over-fixed and saving the 

 ovary itself from that fate. The figures from Flemming and 

 Hermann material are of cells thus protected. 



