PLATE 1 



Fig. 1. Squamous epithelium and cornification in the uterine horn of the rat. 

 38 injections of 80 fig. of estradiol <^;iven as 17-caprylate in the course of 94 days. 

 X 33. (XIV, R. 12; from a series of experiments made in collaboration with E. 

 Egaiia and others.) 



Figs. 2 and 3. Fig. 2. Insular metaplasia of the uterus in the rat. 37 injections 

 of 10 ^g. of estradiol given as 17-caprylate in the course of 91 days. Hypertrophied 

 epithelial cells of the endometrium (uterine"body") siurounding the metaplastic 

 island. Flattened epithelial cells of the endometrium covering the metaplastic 

 island, x 84. (XIV, R. 6.) Fig. 3. Cylindric epithelial masses in the stroma of the 

 mucosa of the uterine horn of the rat. 38 injections of 80 jj.^. of estradiol given as 

 17-caprylate in the comse of 94 days. Proliferation is probably at the expense of 

 uterine glands. Flattened epithelial cells of the edometrium cover the cylindrical 

 epithelial masses, x 67. (XIV, R. 15; same series as fig. 1.) 



Figs. 4 and 5. Epithelial proliferation of "precancerous" aspect in the endo- 

 metrium of the upper third of uterine horn in the guinea pig. 100 injections of 

 20 fig. of estradiol given as 3-benzoate in the course of 245 days; sacrificed 1 14 days 

 after stopping injections. Fig. 4. At the top: glandular cysts; at the bottom: 

 extensive epithelial proliferative masses in the stroma beneath the endometrium; 

 .scattered glands in the stroma. Fig. 5. Part of the epithelial masses at higher 

 magnification (I, 14; from a series of experiments made in collaboration with 

 R. Iglesias). 



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