CHANGES IN THE NON-PREGNANT UTERUS 107 



by a secretion of mucus, and there is a marked leucooytosis 

 over the entire generative tract. Desquamation of epithelium 

 also occurs in the vagina. Furthermore, emigration of leucocytes 

 between the epithehum of the glands, accompanied by great 

 glandular activity, has been observed by Blair Bell ' in the 

 prooestrous uterus of the rabbit. 



The Cycle in Ungulates 



The uterine changes have been worked out most fully in 

 the case of the sheep. ^ They relate chiefly to the blood-vessels, 

 and are grouped according to four periods as in the case of 

 the monkey, the dog, and the ferret, referred to above. 



(1) Period of Rest. — The histological characters of the uterus 

 during this period are those of an organ in a state of quiescence. 

 Protoplasmic processes can be seen passing from certain of the 

 stroma nuclei, but these, though denser in some places than in 

 others, show httle evidence of division. Dark brown or black 

 pigment may be present in considerable quantities, especially in 

 the region subjacent to the epithehum, both in the cotyledonary 

 papillae and (more frequently) between them and round their 

 bases. Such pigment has not been observed in yearhng sheep 

 (i.e. in sheep less than a year old) ; neither does it appear to 

 occur, as a rule, during the anoestrum, but only during the 

 dioestrous interval. 



(2) Period of Growth. — The nuclei in the stroma multiply, 

 and the mucosa increases slightly in thickness. The epithehum, 

 however, appears to remain unafiected. The blood-vessels in- 

 crease both in size and number, producing uterine congestion. 

 These changes occur both in the cotyledonary papillae and in 

 the intervening tissue around the bases of the papillae. 



(3) Period of Destmction. — The congestion is followed in most 

 cases by the breaking down of some of the vessels. Very fre- 

 quently the first extravasation takes place from vessels situated 

 immediately below certain parts of the stroma where the nuclei 

 are most thickly distributed. Leucocytes are extra vasated 



• Blair Bell, loc. cit. 



' Marshall, " The CEstrous Cycle and the Formation of the Corpus Luteum 

 in the Sheep," PhU. Trams., B., vol. cxcvi., 1903. 



