506 



PHYSIOLOGY OF GONADS 



1000 



750 



500 



Volume 

 (lO^cu.//) 



250 



Normal Cycle 



Cycle After Removal 

 of Corpora Luteo 



Progesterone 

 Treated or Pregnant 



'Corpora Luteo 

 Removed and 

 Oestrin Injected 



Fig. 8.5. The guinea pig follieular cycle and some of its experimental modifications. (After 

 E. W. Dempsey, Am. J. Physiol., 120, 126-132, 1937.) 



or soon after menstruation (Allen, Pratt, 

 Newell and Bland, 1930; Hartman, 1932). 

 In many mammals competent follicles may 

 be present much earlier. Ablation of corpora 

 lutea soon after ovulation in sheep (Mc- 

 Kenzie and Terrill, 1936) and cattle (Ham- 

 mond, Jr., and Bhattacharya, 1944) is fol- 

 lowed in 2 to 4 days by another ovulation, 

 much sooner than in the guinea pig (Fig. 

 8.5). Removal of the primate corpus luteum, 

 at the other extreme, produces no such im- 

 mediate response, judging from the details 

 of three cases among Hartman's (1932) pro- 

 tocols (#40, #41, and #99). Whereas the 

 next ovulations took place earlier than ex- 

 pectation, the intervals between unilateral 

 ovariectomy and ovulation were 16, 14, and 

 22 days, respectively. 



From detailed investigations in the rat, 

 only the earlier stages of follicle growth 

 may properly be regarded as pure FSH ef- 

 fects (Lane, 1935). Lane and Greep (1935) 

 found that addition of Lli to FSH causes a 

 marked increase in the proportion of vesicu- 

 lar follicles to follicles without antra. The 

 use of more highly purified materials 

 ((irecp, van Dyke and Chow, 1942; Fraen- 

 kel-Conrat, Li and Simpson, 1943) has 

 amply confirmed the necessity for combina- 

 tion of the two gonadotrophins to yield max- 

 imal follicle growth and estrogen secretion 

 ill rats. Morphologic evidence indicates that 



LH acts selectively on thecal tissue and, 

 therefore, on the interstitial tissue derived 

 therefrom. Inasmuch as thecal tissue is the 

 presumptive major source of ovarian estro- 

 gen (see below), it follows, perhaps, as Hi- 

 saw (1947) suggested that "the theca in- 

 terna through the action of LH acquires 

 competence to respond to FSH" (by se- 

 creting estrogen) . 



Convincing evidence that thecal tissue 

 and its derivatives are the principal sources 

 of ovarian estrogen was assembled by Cor- 

 ner (1938). The status of this question re- 

 mains essentially the same today. Few endo- 

 crinologists, however, would assume that no 

 other ovarian cells have this capacity (see 

 discussion in the chapter on the ovary). 

 Nevertheless, there is a direct correlation in 

 time between the marked rise in estrogen 

 secretion as the follicular jihase of the cycle 

 advances, on the one hand, and the organi- 

 zation of tlicca interna of the largest fol- 

 licles into organs of obvious endocrine char- 

 acter, on the other. "When especially 

 ])rominent the theca interna is referred to 

 as the "thecal gland" (Mossman, 1937; 

 Stafford, Collins and ]\Iossman (1942). 



Thecal tissue from the multitudes of 

 atretic follicles should not be neglected as 

 a possible additional source of estrogen. 

 From the standpoint of chronologic rela- 

 tions to the cycle tiiis (iiiestioii has hardly 



