98 LEO LOEB. 



very small. A few acini with good cuboidal-cylindrical epi- 

 thelium with a few mitoses; stroma between acini cellular. 

 The animal was apparently for the first time in her life in the 

 period of heat. We see then that all the control guinea pigs at 

 the beginning and at the end of the experiment were perfectly 

 normal; they were sexually mature and underwent the typical 

 sexual cycle. 



2. Undernourished Animals. 



In order to shorten the description of our findings, we shall 

 from now on designate ovaries in which atresia sets in when 

 the follicles are as yet of small or small to medium size as hypo- 

 typical follicles of the first order, and ovaries in which atresia 

 sets in at a slightly more advanced stage of the development of 

 the ovaries, in follicles which have reached or almost reached 

 medium size as hypotypical ovaries of the second order. The 

 uterus is in those cases thin and shows the characteristics de- 

 scribed in the fourth series. We shall designate such a uterus 

 as hypotypical. 



Guinea Pig No. I. 1 Still active at time of examination. Abor- 

 tion had taken place recently. Ovaries showed corpora lutea 

 with marked vacuolization and thick-walled vessels. The vacuo- 

 lization affects all parts of the corpus luteum, but especially the 

 periphery. These are the corpora lutea of the preceding preg- 

 nancy ; following abortion they underwent degenerative changes. 

 Atretic yellow bodies (the remnants of degenerated corpora 

 lutea) ; good small and medium follicles and only an exceptional 

 good large follicle. The large majority of the large follicles 

 showed granulosa degeneration; follicles in various stages of 

 connective tissue atresia. One almost mature follicle. Uterus: 

 Cells of surface epithelium high and large with prominent cyto- 

 plasm; glands with rather high epithelium, but with less 

 prominent cytoplasm; many mitoses in surface epithelium; 

 fibrillar mucosa. At one place there are signs that regeneration 

 had taken place and that a decidua had been present. Mammary 

 Gland: Large. Acini with good cuboidal epithelium and small 

 lumen. Some colloid in lumen. Some large vacuoles in epi- 

 thelial cells. No mitoses. Cellular stroma. Some mononu- 



