590 OF REPRODUCTION. 



much greater tax upon the corporeal powers, than might have been supposed 

 a priori ; and it is a well-known fact, that'the highest degree of bodily vigour 

 is inconsistent with more than a very moderate indulgence in sexual inter- 

 course ; whilst nothing is more certain to reduce the powers, both of body and 

 mind, than excess in this respect. These principles, which are of great 

 importance in the regulation of the health, are but results of the general law, 

 which prevails equally in the Vegetable and Animal kingdoms, that the 

 Development of the Individual, and the Reproduction of the Species, stand in 

 an inverse ratio to each other. 



III. Action of the Female. 



739. The essential part of the Female Generative System is that in which 

 the Ova are prepared ; the other organs are merely accessory, and are not to 

 be found in a large proportion of the Animal kingdom. In many of the lower 

 animals, the Ovaria and Testes are so extremely like each other, that the dif- 

 ference between them can scarcely be distinguished ; and the same has already 

 been stated regarding the condition of these organs in Man, at an early period 

 of development ( 697 b). The fact is one of no small interest. In the lower 

 animals, the Ovarium consists of a loose tissue containing many cells, in which 

 the Ova are formed, and from which they escape by the rupture of the cell- 

 walls ; in the higher animals, as in the Human female, the tissue of the Ova- 

 rium is more compact, forming what is known as the stroma ; and the Ova, 

 except when they are approaching maturity, can only be distinguished in the 

 interstices of this, by the aid of a high magnifying power. We owe to Dr. 

 Barry the discovery of the earliest stages in the production of the Ovum and 

 its accessory parts, in Mammalia and other Vertebrata. In order to understand 

 his account, however, it will be necessary that the parts of which the ovum 

 consists should be previously understood. Taking the Fowl's Egg as a fami- 

 liar illustration, it must be remarked, in the first place, that neither the albumen 

 which forms the white, nor the shell-membrane with its testaceous covering, 

 exists in the Ovarian Ovum ; xthese portions being added during its passage 

 along the oviduct. The parts which we have to analyze, are the Yolk-mem- 

 brane and its contents. Within the Yolk-membrane we find, in the first place, 

 the Yolk itself ; a substance consisting in part of albuminous granules, and in 

 part of oily globules. Towards the centre, the character of the Yolk in some 

 degree changes ; its colour being lighter, and the granules presenting more 

 the appearance of cells, with minuter globules in their interior. The central 

 portion is termed the discus vitellinus. Occupying the centre of the yolk 

 (in the immature ovulum) is a large cell, very distinct in aspect from the 

 rest, and having a well-marked nucleus upon its walls. This is termed the 

 germinal vesicle; and the nucleus, the germinal spot. The Mammalian 

 Ovum contains exactly the same parts ; but the yolk is much smaller in pro- 

 portion, and corresponds in character rather with the discus vitellinus than 

 with the whole yolk of the Bird's egg. The Ovum in all Vertebrated animals 

 is produced within a capsule or bag, the exterior of which is in contact with 

 the stroma of the ovarium ; this has been termed in Mammalia, the Graafian 

 follicle, after the name of its first discoverer ; but the more general and appro- 

 priate designation of Ovisac has been given to it by Dr. Barry, who has shown 

 that it exists in other classes of Vertebrata. Between the Ovum and the 

 Ovisac, in Oviparous animals, there is scarcely any interval ; but in the Mam- 

 malia, a large amount of granular matter is present ; and this arranges itself 

 into some peculiar structures discovered by Dr. Barry, and presently to be 

 described. The membrane which surrounds the yolk in Mammalia has re- 

 ceived, on account of its thickness and peculiar transparency, the designation 



