70 W. B. Kirkham — Maturation of the Eg(/ of the White Mouse. 



21 days, a large number of male and female white mice were placed 

 together in a suitable cage, and the females then examined at fre- 

 quent intervals for signs of pregnancy. As soon as such indications 

 appeared, those females were mated, and close watch was kept for 

 litters of young. The females were killed at various stages of 

 pregnancy, careful records being kept of the exact time of parturi- 

 tion. After being chloroformed the bodies were quickly opened, 

 and the ovaries with the Fallopian tubes were cut out ; while in 

 some instances these parts were used for the examination of living 

 eggs, in others they were at once placed in a killing fluid. The kill- 

 ing fluids used were strong and weak solutions of Flemniing, cor- 

 rosive acetic acid, picro-acetic acid, and Zenker's mixture. 



For general work Zenker's mixture has given by far the best 

 results, owing largely to the great rapidity with which it penetrates, 

 and to its not blackening the tissues as do osmic mixtures. The 

 strong solution of Flemming, and picro-acetic acid, are excellent 

 for spindle fibers. Corrosive acetic acid gives fairly good results, 

 while the weak solution of Flemming is decidedly unsatisfactory, 

 owing to its poor penetration. 



After being killed and dehydrated, the tissues were imbedded in 

 paraftine and sectioned •008"'"' thick. The sections were then aftixed 

 to slides with Ma^'cr's albumen, and stained, for preliminary study, 

 fifty slides at a time, with Delafield's haematoxylin and orange G. 

 This method of staining is a simple process, but is all that is 

 necessary to enable one to examine a series for karyokinetic figures ; 

 when such were found the sections were decolorized with acid 

 alcohol, and restained with Heidenhain's iron haematoxylin. 



The technique of obtaining living eggs is very simple, and the^^ 

 were seen and studied by Tafani ('8o), although he makes no mention 

 of the method used to obtain them. A female mouse is killed at 

 the time when ovulation is thought to have taken place, tiie ovary 

 and Fallopian tube are removed from the body, placed upon a glass 

 slide on the stage of a dissecting microscope, freed, as far as possi- 

 ble, from fat and connective tissue, and then gently teased up with 

 fine needles until the eggs are seen to drop out. When found, the 

 eggs can be transferred on the slide to the stage of a compound 

 microscope for more detailed examination and study. Karyokinetic 

 figures and nuclei can be brought out by the use of acetic-carmine. 



The results obtained have been briefly stated in a preliminar}^ paper 

 (Kirkham '.0^), and a brief summary has appeared in Science (Coe 

 and Kirkham, :07)- The ovaries of every mouse examined during 



