MAMMALIAN OVARY 



455 



gen wliich feeds back to stimulate further 

 growth of the meinbrana granulosa and fol- 

 licle. 



Attractive as such a hypothesis is, it has 

 at least one weakness. If gonadotrophic 

 extract rich in FSH is administered to im- 

 mature rats for three days, there is a gen- 

 eralized stimulation of granulosa tissue 

 (Fig. 7.3). Small follicles increase in size, 

 medium sized follicles develop an antrum, 

 and Graafian follicles become large and 

 vesicular (Parkes, 1943), but ovulation is 

 uncommon. At autopsy the ovaries are pale 

 and edematous. The ovaries are markedly 

 increased in size from numerous follicles be- 

 coming vesicular. Histologically there is 

 little stimulation of the theca interna. Gaar- 

 enstroom and de Jongh (1946) recog- 

 nized this ovarian response when they 

 suggested that FSH be designated as Ge 

 (gonadotrophin e])ithelial). This tissue re- 

 sponse offers evidence that FSH is primarily 

 f'oncerned with growth and proliferation of 

 the granulosa cells, but there is no explana- 

 tion to account for the failure of these 

 granulosa cells to stimulate the differentia- 

 tion of the theca interna and the eventual 

 secretion of estrogens. 



During all of follicular growth, the pres- 

 ence of estrogen has come to l^e assumed and 

 its production by the growing follicle is 

 thought to begin with the appearance of the 

 theca interna (see below). On the other 

 hand, the amount produced and the rate of 

 production are unknown. The amount must 

 increase with the growth of the follicles. 

 Gillman and Gilbert (1946) found during 

 their investigation of perineal turgescence 

 in the baboon that, once the perineum 

 reaches maximal turgescence, additional 

 estrogen is required to maintain it. They 

 concluded that in normal animals, during 

 the second part of the phase of turgescence, 

 there must be an increased output of ovarian 

 estrogen. Direct studies have yielded little 



similarly suggestive. Autografts of ovarian medulla 

 without cortical tissue or oocytes, and autografts of 

 cortical tissue were transplanted to various sites in 

 .sexually mature rabbits. The grafts of cortical tis- 

 su(> p(>rsisti'(l after the medullary grafts had disap- 

 peared. Ingram concluded that medullary tissue 

 containing interstitial tissue but no follicles can- 

 not survive. 



information. Foi'd and Hirschman (1955) 

 estimated alkaline phosphatase activity in 

 the ovary of the rat, but the concentrations 

 in the theca interna and ovarian tissue as 

 a whole were relatively constant during the 

 phases of the cycle. 



B. GROWTH OF VESICULAR FOLLICLES 



The growth of the follicle which is de- 

 pendent on stimulation by hypophyseal gon- 

 adotrophins has been described for a number 

 of animals and, for a few (cow, sow, ewe, 

 guinea pig, rat) plotted with respect to the 

 time of the preceding ovulation (McKenzie, 

 1926; Hammond, 1927; Grant, 1934; Myers, 

 Young and Dempsey, 1936; Boling, Blan- 

 dau, Soderwall and Young, 1941 ; von Burkl 

 and Kellner, 1956). Data of the latter sort 

 are especially valuable for the baselines 

 they provide for experimental studies of the 

 factors affecting the pituitary-gonadal re- 

 lationships. Deviations in the shape of the 

 curve of follicular growth, and disparities 

 in the size of the growing follicles and in the 

 size and structure of the corpora lutea, are 

 clear indicators of abnormalities in function 

 which have been too little used. 



C. PREOVULATORY SWELLING 



Without exception in the animals listed 

 above, and probably in the horse, goat, and 

 bat, if we may judge from the data pre- 

 sented by Hammond and Wodzicki (1941), 

 Wimsatt (1944), and Harrison (1946, 

 1948b), a linear period of growth during 

 most of the diestrum is followed by a posi- 

 tive acceleration (preovulatory swelling) ; 

 shortly before estrus and ovulation. The 

 point at which this acceleration occurs is 

 the point in the development of the follicle 

 where physiologic evidence for the produc- 

 tion of progesterone by the unruptured fol- 

 licle was first found (Dempsey, Hertz and 

 Young, 1936; Astwood, 1939). As we will 

 see later, however, the ^'moment" the pre- 

 ovulatory swelling begins is not necessarily 

 the point in time when the first progesterone 

 is produced. 



In most sjiecies in which the course of 

 the preovulatory swelling has been followed, 

 it is a 10- to 12-hour process (Hammond, 

 1927; Grant, 1934; Myers, Young and 



