47! 



PHYSIOLOGY OF GONADS 



Harrison, Harrison-Matthews and Row- 

 lands, 1951; Amoroso and Rowlands, 1951), 

 but an unusual structural condition is found 

 in these ovaries. No vesicular follicles are 

 present and the ovaries, which are larger 

 than those of the adult, are composed mostly 

 of interstitial tissue which is enclosed by a 

 thin cortex containing short chains of germ 

 cells and a few oocytes surrounded by a sin- 

 gle layer of epithelial cells. Comparable in- 

 formation does not exist for the seal, but in 

 the horse the development of this condition 

 is reached during the estrogenic phase and 

 after the gonad-stimulating hormone is no 

 longer detectable in the blood of the preg- 

 nant adult. As a result, and cjuite apart from 

 the belief that serum gonadotrophin does 

 not cross the placenta (Amoroso and Row- 

 lands, 1955 j, the massive interstitial tissue 

 liyperplasia is thought to have been stimu- 

 kited by estrogenic rather than by gonado- 

 trophic action. 



The immediate jiostpubertal jieriod and 

 middle age are periods of relative stability. 

 The period of old age has been too little 

 studied and is in need of attention. In old 

 mice the ovaries are reported to become 

 unresponsive to exogenous gonadotrophin 

 (Green, 1957). Ortiz (1955), on the other 

 hand, stated that although a certain degree 

 of ovarian sensitivity is lost in old ham- 

 sters, there is a surprising degree of re- 

 sponsiveness present until death, not only 

 after the animal is no longer fertile, but 

 even in animals with ovaries almost com- 

 pletely atrophic. 



In young animals and in old animals there 

 are irregularities of ovarian function and 

 irregularities in the character of the cycles 

 which probably can be related to imbalances 

 in the pituitary-ovarian relationship. In 

 polytocous sjK'cies, fewer follicles ovulate 

 in young animals (Young, Dempsey, JMyei-s 

 and Hagquist, 1938; Ford and Young, 1953, 

 the guinea pig; Perry, 1954, the domestic 

 pig; Ingram, Mandl and Zuckerman, 1958. 

 the mouse and rat), and in old animals 

 (Perry; Ingram, Mandl and Zuckerman). 

 These statements of fact, iiowcx-cr. do not 

 reveal what is presumed to be more im- 

 portant. In young and old animals the na- 

 ture of tlie irregularities, particularly those 

 of ovarian function, seem to differ. Evidence 

 collecte(l fi'om rhesus monkeys (Hartman, 



1932) and chimpanzees (Young and Yerkes, 

 1943) suggests follicular growth without 

 ovulation and luteinization, or in the guinea 

 pig a sluggishness of follicular growth which 

 is followed by ovulation and the forma- 

 tion of functional corpora lutea (Ford and 

 Young, 1953) . In old animals there may also 

 be abnormalities of follicular growth, but 

 as the numerous reports are read, the im- 

 pression is given that abnormalities of 

 luteinization are more prominent (Deanesly, 

 1938b; Wolfe, 1943; Wolfe and Wright, 

 1943; Loci), 1948; Thung, Boot and Miihl- 

 bock, 1956; Dickie, Atkinson and Fekete, 

 1957; Green, 1957). Additional investigation 

 will be necessary before we can be sure 

 that the pituitary-gonadal imbalance in 

 young animals differs from that in old ani- 

 mals. On the whole, the possibility seems to 

 have received little attention, but its im- 

 portance justifies more careful study. 



VII. Other Endocrine Glands and 

 the Ovaries 



A. THYROID 



The relationship of the thyroid to the 

 functioning of the ovaries was one of the 

 first subjects of modern endocrinologic in- 

 vestigation. Notwithstanding, disappoint- 

 ment must be expressed that after more 

 than 50 years of effort, little more than 

 cautious generalization is possible. This 

 admission is not a confession of defeat; to 

 be sure, there is an unfortunate number of 

 uncertainties, but we have come to know 

 what is necessary in the way of experi- 

 mental design and techniques to enable us 

 to proceed with the confidence that a grati- 

 fying clarification can be achieved. The 

 greatest obstacle could be, not the lack of 

 means, but rather the failure to use the 

 means which are alnmdantly at liand for 

 more coordinated eft'orts than many which 

 lia\e cliaracterized this field in the past. 



The general l)elief that the thyroid is in- 

 voh-ed in reproductive function is grounded 

 in two categories of observations. The first 

 includes those demonstrating that ovarian 

 lioi'inones exert an action on the thyroid. 

 'I'lieic lia\-e been many I't'ports that in the 

 human female the thyi'oid enlarges at pu- 

 berty, at menstruation, and during preg- 

 nancy (Gamier, 1921; Marine, 1935; Neu- 



