456 



PHYSIOLOGY OF GONADS 



Dempsey, 1936; Doling, Blandau, Soder- 

 wall and Young, 1941 ; Rowlands and Wil- 

 liams, 1943; Rowlands, 1944), although in 

 the cat and ferret the process is triggered 

 by mating and extends over 25 to 30 hours. 

 The preovulatory swelling can be initiated 

 by injecting gonadotrophins of the LH or 

 ICSH type, but they are effective only on 

 well matured follicles (Hisaw, 1947; Tal- 

 bert, Meyer and McShan, 1951). The 

 younger follicles are not stimulated and, on 

 the contrary, they may show an accelerated 

 atresia. It could be postulated that the fol- 

 licules with well developed theca interna 

 were "competent" and that stimulated theca 

 interna produced estrogen which favored 

 the development of these follicles. The 

 smaller follicles were "incompetent" in the 

 absence of a thecal investment and became 

 atretic. If HCG is injected into immature 

 rats, the theca interna around the vesicular 

 follicles hypertro])hies within 24 hours and 

 these follicles enlarge rapidly. The vaso- 

 dilation of the theca blood vessels is grossly 

 evident within a few hours (Kupperman, 

 McShan and Meyer, 1948; Sturgis and 

 Politou, 1951; Odcblad, Nati, Selin and 

 Westin, 1956). 



Explanation has been sought for the na- 

 ture of the changes within the follicle which 

 lead to the accelerated enlargement culmi- 

 nating in ovulation. Studies of the staining 

 qualities of such follicles reveal that the 

 metachromatic polysaccharides of the gran- 

 ulosa (hyaluronic acid and chondroitin 

 sulfuric acid) become progressively depoly- 

 merized and orthochromatic. This hydroly- 

 sis of the mucopolysaccharides gives rise to 

 an increased osmolarity which may be the 

 major factor in the preovulatory swelling of 

 the follicle (Harter, 1948; Catchpole, Gersh 

 and Pan, 1950; Odeblad, 1954; Zachariae, 

 1958; Zachariae and Jensen, 1958; Jensen 

 and Zachariae, 1958). Accompanying the 

 swelling is a dispersal of the cells of the 

 cumulus oophorus. This may be a cons(^- 

 quence of the breakdown of the intcrcclhihii' 

 substance in the stinudated niciubraiia gi'aii- 

 ulosa. 



The time r('(|uirc(l for follicular growth 

 and maturation fi'oin the stage when its 

 further development is dependent on pitui- 

 tary gonadotrophin stimulation to ovulation 

 is related to the length of the cycle and 



therefore varies greatly from species to spe- 

 cies. Somewhat less than 4 to 5 days are re- 

 quired in the rat (Boling, Blandau, Soder- 

 wall and Young, 1941 ) , somewhat less than 

 16 days in the guinea pig (Myers, Young 

 and Dempsey, 1936), somewhat less than 

 21 days in the cow (Hammond, 1927), and 

 ])resumably comparable intervals in other 

 species. Vermande-Van Eck (1956) esti- 

 mated that in the rhesus monkey the aver- 

 age time required for the growth of a mature 

 follicle from the large follicle without an 

 antrum is 4 to 6 weeks; 11 days are esti- 

 mated to lie necessary for the complete de- 

 velopment of a follicle in the rabbit (De- 

 saive, 1948) . Ovulation occurred earlier than 

 normal when the corpora lutea from the 

 ])receding cycle were removed, but the rate 

 of follicular development was not altered 

 (Dem])sey, 1937). Presumptive evidence ex- 

 ists, however, that the rate of growth may 

 be slower in pubescent chimpanzees (Young 

 and Yerkes, 1943), baboons (Gillman and 

 Gilbert, 1946), and guinea jngs (Ford and 

 Young, 1953). 



D. OVULATION 



Ovulation, under normal circumstances, 

 ))robably is explosive (Hill, Allen and 

 Kramer, 1935, in the rabbit; Blandau, 1955, 

 in the rat). In 1 of 2 human i)atients Doyle 

 (1951) saw a gush of follicular fluid at the 

 time of ovulation. In 163 ovulations timed 

 l)y Blandau the interval between the rupture 

 of the stigma and the escape of the ovum 

 was 72 seconds when most of the folliculai' 

 fluid escai)ed in advance of the ovum, and 

 216 seconds when the cumulus oophorus pre- 

 ceded the follicular fluid. The slower, steady, 

 continuous flow of the liquor folliculi which 

 has been described by Walton and Ham- 

 mond (1928) in the cow, Markee and Hin- 

 sey (1936) in the rabbit, and by Doyle 

 (1951) in one human sul)ject could be an 

 artifact of the procedures used in watching 

 the jM'Ocess. 



The mechanisiu heading up to formation 

 of the stigma and rupture of the follicle is 

 unknown. Claesson (1947), using the sub- 

 microscoi)ical differences which can be ol)- 

 served in ])olarized light, distinguished 

 smooth muscle from connective tissue cells 

 and rep()rte(l that no bundles of smooth 

 muscle or isolated cells were found in the 



