302 EDGAR ALLEN 
accumulation of data as to cycle length, examination once daily 
was found to be adequate. The condition of the vulva, the 
degree of opening of the vagina, and the nature of the vaginal 
contents were noted. A histological examination of the smears 
was always the deciding factor in the diagnosis. Smears were 
made by the usual bacteriological technique. Haematoxylin 
and aqueous eosin were used as stains. <A block with a converg- 
ing trough which could be quickly covered was devised for 
holding the animal while smears were being taken. 
Animals used for correlating the conditions of different parts 
of the genital tracks with each other and with the cellular changes 
in the smears were examined and smears collected for several 
cycles before they were killed. ‘These repeated examinations 
gave some indication of their ‘degree of sexuality.’ Smears 
were invariably taken immediately before killing. The animals 
were killed instantly by a sharp rap at the base of the skull, 
the abdominal cavity opened, and the conditions of the uterine 
cornua noted as to size, transparency, blood supply, and con- 
tractility. Shortly after the body cavity is opened, the uterus 
contracts to such an extent that the marked differences present 
at various stages in the cycle cannot be detected; therefore, an 
immediate inspection is necessary. After examining the fresh 
uterus the bladder was clipped off, the symphysis pubis sectioned, 
the skin was cut around the vulva, and the phallus, vagina, 
uterus, oviducts, and ovaries were dissected out and placed on a 
glass slide. After a minute’s drying they adhere to the slide and 
can be fixed without contortion. Bouin’s fluid was used as a 
fixing reagent and proved satisfactory for both uteri and ovaries. 
After hardening in the lower alcohols, the organs were cut 
to facilitate orientation and imbedding. Serial sections 10.4 
thick were made of the ovaries and oviducts. In trimming these 
organs it is important that the peritoneal ovarian sac be left 
intact to protect the surface of the ovary during dehydration 
and imbedding. Several transverse serial sections of the middle 
of each uterine cornu, the body of the uterus, the vagina, and the 
cervix, as well as several serial sagittal sections through the 
phallus and lower vagina, were cut at a thickness of 6 to 8u. 
