VAGINAL EPITHELIUM OF GUINEA-PIG 433 
was placed in front of the animal’s left hind leg and exerted 
pressure just in front of the vulva; at the same time with the left 
forefinger between the vulva and the right leg, it was easy slightly 
to open the orifice of the vagina. The syringe, containing about 
1 ec. of warm, normal, salt solution, was then introduced into the 
vagina to a depth of 25 to 40 mm. By squeezing the bulb and 
forcing the contents of the syringe into the vagina once or twice, 
it was possible to get a characteristic sample of the cells in the 
lumen. If, while withdrawing the syringe, pressure was applied 
anterior to the vulva with the thumb of the left hand, the sample 
could be drawn up readily into the syringe. Enough of a sample 
was obtained at one operation by this method to make several 
smears. This proved a most satisfactory method, because each 
time a sample was taken the vagina was washed out and the cells 
which were free in the lumen were removed; consequently, it was 
reasonable to suppose that all of the cells which were found in any 
one sample had been shed during the interval immediately follow- 
ing the preceding sample. 
In order to study the cycle, samples were taken at 8 A.M., 12 M., 
4 p.m., and 8 p.m., and the results recorded. Animals were then 
killed during each stage as revealed by the character of the smears. 
A small amount of 0.75 per cent solution of table salt immediately 
followed by Bouin’s fixing fluid was injected under pressure pos- 
teriorly into the aorta just anterior to the diaphragm. By this 
method the vagina in situ was fixed in its normal position at the 
earliest possible moment and its excision greatly facilitated. 
After removal from the body the vagina was immersed twenty- 
four hours longer in the fixing fluid. Most of the picric acid was 
extracted in 50 per cent alcohol containing lithium carbonate. 
Portions of the vagina including the cervix were then dehydrated, 
cleared, and imbedded in paraffin and sectioned at 7jy. The 
condition in the vaginae as revealed by these sections was then 
correlated with the smears taken just before killing the animal. 
The uterine glands in the guinea-pig secrete an abundance of 
mucus which flows down into the vagina (Stockard and Papani- 
colaou, 717), often obscuring the nature of the smear. Indeed, 
Stockard and Papanicolaou found uterine epithelial cells thus 
