OVARY (FUNCTIONS). 



553 



in the ovary remain, and no new ones are 

 supenidded, there will still be more than 

 sufficient for all the purposes of reproduction. 

 But as the functional activity of the ovary, so 

 far as relates to the emission of ova in a state 

 fit for impregnation, is restrained on the one 

 side until the arrival of a certain stage of 

 development of the parent, so on the other 

 a period equally arrives, after which this power 

 of producing and emitting ova altogether fails; 

 and it is plain that both these restrictions con- 

 tribute to one and the same end, the limita- 

 tion, namely, of the office of reproduction to 

 that period of life in which the vital energies 

 of the producing body, having attained to full 

 perfection, remain still unimpaired, so that 

 the qualities of health and vigour in the parent 

 may be transmitted undimiuished to the off- 

 spring. 



From this it results that the ovary in Man, 

 as well as in the Mammalia generally, has 

 three noticeable periods : the first, of prepara- 

 tion ; the second, of activity ; and the third, of 

 decay : and these correspond respectively with 

 the periods of infancy and childhood, of youth 

 and prime, and of decline and old age. 



The condition of the ovary at each of these 

 epochs will be traced ; but the middle period 

 is obviously that to which the chief interest 

 attaches. 



During certain portions of this epoch, and 

 in some instances through more or less of its 

 whole extent, the ovary is employed in ripen- 

 ing and emitting ova. In this respect, how- 

 ever, greater variation is perceptible in dif- 

 ferent species than in any other particular. 

 But in all alike this one circumstance is ob- 

 servable, namely, that the emission of ova is a 

 periodic occurrence. 



Now the periods of emission of ova may so 

 occur as to make the times of parturition co- 

 incident with the returns of those seasons 

 which are most favourable for the rearing of 

 the young. In such cases the capacity for 

 impregnation may be limited to one period of 

 the year, the ova being ripened and emitted 

 only at that time. The roe affords an inter- 

 esting example of this. The doubts which 

 have been sometimes entertained as to the 

 precise time at which the roe becomes impreg- 

 nated have now been settled by the recent 

 very careful researches of Bischoff *, who has 

 proved that this occurs at the end of July and 

 during the month of August, and that it is 

 only then that the ovaries of the female con- 

 tain ripe ova, and the testes of the male ripe 

 semen. At other times these are not to be 

 found ; hence it follows that in this animal im- 

 pregnation is impossible at all other seasons. 



But in many animals the periods of ripening 

 and discharge of the ova recur with much 

 greater frequency ; and probably climate, food, 

 domestic care and the like, exercise a certain 

 degree of influence in modifying the returns of 

 these periods. 



In the human female the same periodicity is 

 observable; and it is now rendered in the high- 



* Knlwick. Jos Relics, 1854. 



est degree probable that in her case the times 

 of ripening and generally of the discharge of 

 the ova are coincident with the times of 

 menstruation *, just as it has been proved 

 beyond dispute that in other Mammalia the 

 same process accompanies that more obvious 

 condition of aptitude and desire for sexual 

 intercourse to which the terms oestrus and 

 rut are applied. 



A periodical maturation, therefore, of ova, 

 accompanied by dehiscence of the ovicapsules 

 and discharge of their contents, may be said 

 to constitute the principal offices of the ovary 

 during the prime of life. But notwithstanding 

 that these processes are periodically performed, 

 the ovary cannot at any time be said to be in 

 a condition of perfect rest, except under cir- 

 cumstances which will be presently noted; for 

 whilst some ovisacs may be observed to be 

 advancing and preparing to emit ova, others 

 may be seen receding or becoming obliterated. 

 The climax, however, of each serial process 

 is the dehiscence or rupture of one or more 

 follicles. Upon this the whole force of the 

 ovary is, as it were, for the time concentrated. 

 This event being terminated, the activity of 

 the ovary passes away as regards that parti- 

 cular follicle. Enough, however, of vital 

 energy remains in the now useless part to suf- 

 fice for the healing of the wound, and the 

 closing and obliteration of the cavity left after 

 the escape of the ovum. But the blood gra- 

 dually deserts the walls of the previously 

 congested ovisac, the distended vessels in its 

 neighbourhood shrink and become obliterated, 

 and the action is transferred to another set of 

 follicles, one or more of which pass through a 

 similar order of changes. 



Two circumstances, however, arrest for a 

 time this process. The one is the occurrence 

 of utero-gestation, the other the performance 

 of lactation ; and although occasional excep- 

 tions may be observed, yet so far as this ques- 

 tion has been examined, the evidence collected 

 favours the belief, that in pregnant women and 

 in those who suckle, no ova are emitted during 

 the continuance of either of these processes.-]- 



This view also, so far as relates to lactation, 

 receives support from the well-known circum- 

 stance that a considerable degree of immunity 

 from impregnation occurs during the conti- 

 nuance of lactation, a circumstance easily ex- 

 plained upon the supposition that at that time 

 usually no ova are matured or emitted. 



It will now be necessary to trace in detail 

 the process of ovulation, so far as regards the 

 structures concerned in that process which 

 properly belong to the ovary. 



A general account of the Graafian follicle 

 in its mature state having been already given 

 at p. 550., the changes which this important 

 structure undergoes at different periods of its 

 development and decay will now be examined. 



* The question of the connection between men- 

 struation and the maturation and discharge of ova 

 from the ovary, is considered under the head " Men- 

 struation " at page CCG. 



f Negrier, Kecherdies sur les Ovaires, chap, ii. 

 iii. 



