152 THE PHYSIOLOGY OF REPRODUCTION 



of the liquor folliculi. On the other hand, there may be practically 

 no haemorrhage, or the discharged blood may be expelled to the 

 exterior of the ovary (with the greater part of the liquor), remain- 

 ing as a small clot upon the surface. 1 It would seem probable 

 that the vessels burst as an effect of the released tension conse- 

 quent upon the rupture of the follicle ; but, as already mentioned, 

 it has been suggested that possibly the latter process may itself 

 occur as the result of the pouring out of blood into the 

 cavity. During the early stages of formation of the sheep's 

 corpus luteum leucocytes of the polymorph variety have been 

 observed in great abundance, but in the later stages they 

 disappear, some of them undergoing degeneration. These 

 leucocytes are not extravasated, but wander inwards with the 

 growing strands of connective tissue. 2 Their occurrence should 

 probably be associated with the necessity to dispose of the 

 blood-clot when such is present. 



The ingrowth of connective tissue commences a very short 

 time after ovulation, and in the sheep may be seen very dis- 

 tinctly as early as in the seven-hour stage of development. 

 Blood-vessels are carried inwards with the connective tissue, 

 and these undergo multiplication, so that the corpus luteum is 

 a highly vascular structure. 



If the discharged ovum fails to become fertilised the corpus 

 goes on growing for a short time and then degenerates, so that, 

 in the case of the human female, two months after ovulation 

 it is reduced to the condition of an insignificant cicatrix. In 

 the smaller animals it disappears after a considerably shorter 

 time. If, on the other hand, conception succeeds ovulation, the 

 corpus luteum continues to increase in size until almost the 

 middle of pregnancy, and in the human female attains to a 

 diameter of nearly an inch in length. 



The large size of the completely developed corpus luteum 

 is the more remarkable in that it results to so large an extent 

 from the simple hypertrophy of certain of its constituent cells. 



1 It is sometimes stated that the haemoglobin of the blood-clot is trans- 

 formed into the yellow pigment (known as lut-ein) which gives the luteal cells 

 their characteristic colour ; but this is obviously incorrect, since there may 

 be no blood-clot in the follicle, whereas the luteal cells always contain 

 lutein. 



2 Marshall, Phil. Trans., loc. cit. 



