CYCLIC CHANGES IN THE OVARIES AND UTERUS OF THE SOW, ETC. 137 



others seem to be impeded by their neighbors from reaching the free surface. The 

 cells are small, since there is a relatively low proportion of cytoplasm to nucleus; 

 so that, taking all these criteria together, a histologist coming upon such a tissue 

 for the first time might perhaps class it among epithelia like those of the urinary 

 bladder rather than among the secretory types of epithelial tissues. 



Three details are especially to be noted at this stage: First, mitotic figures 

 are very numerous in the epithelium, in some specimens occurring as often as 1 in 

 every 50 nuclei. The epithelium, therefore, is actively proliferating. Second, a 

 contrary process is also indicated by the presence here and there of phenomena of 

 degeneration; at the base of the epithelium there are points where two or three 

 cells have become vague of outline, with chromatolysis of the nuclei, so that a small 

 vacuole is formed in which lie a few nondescript nuclear fragments or granules 

 (fig. 26, pi. 4, v. d.~). This degeneration is, as we shall see, merely the latter stage 

 of a phenomenon which sets in slightly earlier than the period of oestrus. The 

 same may be said of the third fact of especial interest, namely, the presence, in 

 large numbers, of neutrophilic polymorphonuclear leucocytes in the subepithelial 

 connective-tissue, and even of a few which are embedded in the epithelium, pre- 

 sumably making their way into the lumen (figs. 25, 26, pi. 4, p. m.). 



During oestrus the stroma of the uterus, in mature animals, is very edematous, 

 so that the interspersed cells are widely spaced (fig. 20, pi. 3). 



There are a few mitoses in the cells of the superficial gland tubules, but none 

 in those of the deep glands. A curious feature is the presence, in some of the 

 gland cells, of highly chromatic extra-nuclear granules, reaching a diameter of 1 to 

 2 micra. The nuclei of cells possessing these granules are usually of normal ap- 

 pearance; but I have tentatively considered the granulation as a degeneration 

 phenomenon affecting a few cells of the glands. It is seen only during the cestrous 



period. 



TRANSITIONS DURING FIRST WEEK AFTER OVULATION. 



(Figure 27, plate 4.) 



During the first week after ovulation we see the onset of changes which finally 



effect a striking alteration in the form of the surface epithelium. The individual 



cells at first merely grow larger, so that the layer which they 



Ova in transit through . , . , , . 



the Fallopian tubes; then form is further piled up to a thickness reaching ,35 to 50 micra. 

 in the uterus, where they -phe yacuolar spaces indicative of degeneration disappear 



degenerate about the . 



seventh or eighth day. by the end of oestrus, and by the time the eggs have passed 

 Had they been fertilized t ^ uterus there are no more polymorphonuclear neutrophil 



the ova would now be . 



passing through the stages leucocytes to be seen in the epithelium or subepithelial stroma. 

 "he Mitotic divisions of the surface epithelium continue to be very 



corpora lutea are in pro- numerous until the end of this period, when they cease alto- 

 gether, not to be seen again until just before the next oestrus. 

 About the time of their cessation there is a further change in the morphology of the 

 surface epithelial cells, which have been growing in height and which at last are 

 somewhat suddenly ranged into a simple, high columnar epithelium, which will be 

 described in the next section. 



