358 



one with another and a very considerable network of small sinus-like 

 blood vessels is soon developed. 



It is in the luteal cells however, that the alteration in this stage 

 is most marked. They undergo a further enlargement without sign 

 of direct or indirect division, causing the central plug of connective 

 tissue to be somewhat reduced and their cytoplasm assumes the 

 granular appearance so characteristic of glandular cells in activity. 



This growth of fresh connective tissue and swelling of the luteal 

 cells causes the corpus luteum as a whole to increase considerably 

 in size and in consequence the ovarian ' stroma becomes very much 

 reduced. In this case too, it is impossible to estimate the time 

 occupied by the period of growth, but comparing it with the similar 

 period in the pregnant animal, where the stage of the embryo gives 

 some indication of time, it would appear to be a day or so after 

 its formation. 



Period of constancy. 



After the full growth of the corpus luteum is attained it remains 

 constant in size for some time before it is gradually absorbed. 

 According to Sandes it remains in the same state for seven or eight 

 weeks before it begins to decline. 



No record is available to show how long the corpora lutea 

 persists in non-pregnant animals, but there are reasons for thinking it 

 to be a considerable time. It has been pointed out previously (15) 

 that they are present in such animals at a time when the mammary 

 gland corresponds in development to that in a pregnant doe thirty- 

 six hours after the birth of the young. Again in animals twenty- 

 five days and twenty-two days after the onset of heat and in one 

 twenty days after copulation (i. e. No. 16) fully grown corpora lutea 

 are to be found which show no signs of beginning to disappear. 



A comparison of the above observations with those made by 

 Sandes will show the close correspondence between the history of 

 the corpora lutea in the two cases. 



It will be seen that in D. viverrinus the formation and growth 

 of the corpus luteum following on ovulation is the same whether 

 pregnancy occurs or not and further there is evidence to show that 

 ovulation is independent of copulation. 



The parts played by the various constituents of the corpus luteum 

 still present several points on which there exist differences of opinion 

 in spite of the amount of work that has been done by different 



