IO LEO LOEI3. 



be at earlier stages still some good medium-sized follicles. There 

 are present one or several mature follicles usually with matura- 

 tion spindle in the ovum of the follicle. Other follicles show 

 early and medium stages of connective tissue atresia. There 

 are usually many follicles in or near the last stage of connective 

 tissue atresia, but the number of such follicles varies and may 

 be relatively small in very young ovaries at the time of the first 

 heat. The structure of the uterus at this period has been de- 

 scribed above (see page i). It is identical with the structure of 

 the uterus in the period of heat when the latter is followed by 

 copulation. Even after extirpation two months previously of 

 the greater part of the uterus, the same phenomena can be ob- 

 served; heat takes place and mature follicles form. The re- 

 maining small part of the uterus forms a little cyst with cylindrical 

 (or cuboidal) epithelium with many mitoses. The gland ducts 

 have highly cylindrical epithelium and also show mitoses. This 

 has been observed in two experiments. Also after almost com- 

 plete extirpation of the thyroid one to two months previously, 

 heat occurs accompanied by the typical changes in the uterus 

 and ovaries. The small remaining part of the thyroid may 

 consist of acini with cylindrical epithelium while the colloid 

 may be almost, or entirely absent. 



At a slightly later period, namely, soon after the rupture of the 

 mature follicles, the condition of the ovaries and uterus is 

 essentially the same; two changes have however, taken place, 

 namely (i) the surface epithelium is not quite so regularly high 

 cylindrical, but may be at certain parts cuboidal; and (2) we 

 find more or less pronounced changes in the surface epithelium 

 and sometimes in the adjoining part of the gland ducts, namely, 

 vacuolization in the epithelial cells; in the vacuoles which press 

 upon the nuclei we may find degenerating cells; chromatin 

 particles may spread over the greater part of the cells. These 

 changes are probably due to the immigration of mononuclear 

 cells or polynuclear leucocytes from the mucosa into the epi- 

 thelium. Here these immigrated cells degenerate. One sees 

 sometimes mononuclear cells immigrating into the epithelium. 

 It is not very probable that the changes in the epithelium follow- 

 ing ovulation are brought about through a disintegration of some 

 epithelial cells. 



