48 INTRODUCTION TO SEXUAL PHYSIOLOGY 



(Hammond). The vagina also undergoes rhythmical changes 

 connected with those of the uterus and ovary during the oestrous 

 cycle. These have been worked out fully by Long and Evans 

 in the polyoestrous rat. When the uterus is distended with fluid, 

 the mucus of the vagina is dry, but subsequently when ovulation 

 has occurred the vaginal lumen contains a cheesy substance, 

 the superficial epithelium and cornified layer of the wall having 

 become completely detached. At a slightly later stage when the 





pig. 





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•^■•■•■•.'■•.'•■•f^t:' •-'". 



Fig. 28. — Section through portion of uterine mucosa of sheep, showing 

 black pigment (p?"^.) formed from extravasated blood. 



ovaries contain developing corpora lutea, and eggs are present 

 in the oviduct, leucocytes are very abundant in the vagina and 

 the surface is moist. Later on the vaginal mucosa returns to 

 the previous condition, the epithelium being entirely re-formed. 

 If pregnancy takes place as a result of coition during oestrus, 

 the corpus luteum in polyoestrous, as with monoestrous mammals, 

 instead of degenerating after a short interval (as with the corpus 

 luteum spurium, as it was called in the older terminology), goes 

 on increasing in size until about the middle of the gestation 

 period, and does not undergo regression till near the close (corpus 

 luteum verum). 



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