368 THE CORPUS LUTEUM OF DASVnirS, 



maternal teats for a period of seven or eight weeks, whilst the 

 period of lactation is prolonged to about four months. 



For the purposes of this investigation the sexes were allowed 

 access to one another, and the date of coitus noted. The females 

 were killed at a varying period afterwards. After securing the 

 blood supply, the internal and external genitalia were removed 

 and the stages of ovum or embrj'o corresponding w^ere noted. 

 The parts were placed in picro-sublimate solution for twenty-four 

 hours and then transferred to alcohols. 



Some were also treated with picro-nitric-aceto-osmic solution. 

 Picro-sublimate fixing fluids were found very satisfactor3\ 



The ovaries were transferred to absolute alcohol, cleared in 

 cedar oil, afterwards put into benzol for 24 hours at a temjDerature 

 of 45° C, to which melted paraffin at 40° C. to 45° C. was 

 gradually added. Finally, the ovaries were transferred to paraffin 

 with the melting point at 50° C, in which they were left at that 

 temperature for a period of two to four hours. This method of 

 embedding gave uniformly good results. 



Sections were cut, some wdth Minot's microtome and some with 

 the rocking microtome. Some were 6 micros, thick, but the 

 majority 10 micros. They were mounted serially and stained 

 according to requirements with Glychsemalum, Glych?emalum 

 with Eosin, Iron-hsematoxylin, and van Gieson's stain after 

 Glychsemalum. This last w^as found particularl}' good for micro- 

 photographs, which were taken with Zeiss' apparatus. 



This paragraph gives the particulars of the material employed. 

 Other ovaries besides those mentioned below w^ere cut, but these 

 were considered to show the most representative stages of develop- 

 ment of the corpus luteum. The stage of ovum or embryo is 

 indicated in each case. 



Ovary, Stage A. 



Ptipe follicles, some showing maturation spindle in the ovum. 



Ovary, Stage B. 



Taken immediately after rupture of the Graafian follicle, ova 

 obtained from uterus before separation of the second polar body. 



This Stage is referred to in this paper as the Polar-body Stage. 



