XIIl] FEMALE GENERATIVE ORGANS 171 



mammary glands (or at anj^ rate ducts) may be found. When 

 present in some quantity, as frequently happens, it gives rise 

 to the condition known as 'seedy-cut,' a term which implies 

 that the bacon of the 'belly-piece' is discoloured. The pigment 

 however is perfectly harmless, and unlike the black pign;ent in 

 the uterus of the ewe (described below) is not blood pigment. 



The season of the year when an animal of an}* species or variety 

 undergoes sexual intercourse has been called by Heape the 

 sexual season for that animal. The actual periods at which 

 copulation occurs are the oestrous periods. These may recur at 

 rhj'thmical intervals within one sexual season as with the mare, 

 the co^\-, the ewe and the sow (polyoestrous animals in Heape's 

 terminology), or there may be onl}'^ one oestrus to the sexual 

 season as with the bitch (monoestrous animals). 



A simple oestrous cycle in an animal of the latter kind (e.g. 

 the bitch) has been divided into a number of jDcriods as follows : 

 Anoestrum^ (period of rest), 

 Prooestrum^ (period of growth and congestion and 



period of destruction). 

 Oestrus (j^eriod of desire). 



Pregnancy Pseudo-pregnancy. 



The complete cycle in the monoestrous dog lasts about six 

 months, there being two sexual seasons and 'heat' periods in 

 one year, these occurring tyiDicall}^ in spring and autumn, but 

 there is some individual variation. In the smaller kinds of dogs 

 the duration of the cycle may be less than six months ^^hile in the 

 larger varieties it ma\' extend over a longer time. 



The anoestrum in the absence of pregnancy lasts for about five 

 months. The generative organs are in a state of quiescence. The 

 ovarian follicles are probably undergoing a slow process of growth 

 and ripening throughout the anoestrum, but they are not con- 

 spicuous upon the surface of the organs, at any rate until the 

 ajiproach of a new heat period. It follows that ovulation does not 

 occur during the anoestrum and the ovaries do not contain corpora 

 lutea. The uterus is relatively anaemic and the glands inactive. 

 The mammary glands also are in a condition of rest unless 

 lactation is going on as a result of recent jjregnancy. 



^ These terms were given by Heape to the periods as above described. 



