TYPES OF (ESTROUS CYCLE 



57 



lactation the uterus becomes much atrophied, presumably owing 

 to the drain on the metabohsm. This atrophy during lactation 

 is in marked contrast to the conditions found in the rat and 

 mouse, in which the uterus is active during lactation owing to 

 the persistence of the corpora lutea. 



Fig. 30. — Photograph of Mammary Gland of Rabbit 



TWELVE DAYS PsEUDO-PrEGNANT. 



Clumps of alveoli have developed along the ducts. 

 (After Hammond.) 



The cyclic changes in the mammary glands of the rabbit are 

 also very obvious. Prior to the first oestrous period the gland 

 consists merely of a few ducts in the neighbourhood of the 

 nipple. At the time of the first oestrous period these ducts grow- 

 out radially for a distance of an inch or an inch and a half round 



