948 OF GENERATION EMBRYONIC DEVELOPMENT. 



independently of the secreting apparatus, being an enlargement of a portion 

 of the pars urinaria of the " urogenital sinus" ( 789). 



788. The essential parts of the Generative apparatus, namely, the Testes 

 in the male, and the Ovaria in the female, are first developed in such im- 

 mediate proximity with the Corpora Wolffiana (Fig. 351, e, e\ that they 

 have been supposed to sprout forth from them ; this, however, is not really 

 the case, as they have an independent origin in the intermediate mass of 

 mesoblastic blastema (termed by Foster and Balfour the genital ridge), 

 from which the Wolffian body and Kidneys have successively been differ- 

 entiated. They make their first appearance in the Chick, as delicate strise on 

 the Wolffian bodies, about the fourth day ; at which period no difference can 

 be detected between the Testes and the Ovaria, which originate in precisely 

 the same manner. The superficial cells proceeding originally from the 

 epi blast acquire special characters, and, as already described ( 737), become 

 invested and inclosed by an outgrowth of the stroma of the ovary, and con- 

 stitute the primordial ova. In the Human embryo, the rudiments of the 

 sexual organs whether testes or ovaria first present themselves soon after 

 the kidneys make their appearance, that is, towards the end of the 7th week. 

 They are originally much prolonged, and seem to consist of a kind of soft, 

 homogeneous blastema, in which the structure characteristic of each organ 

 subsequently develops itself. The Test is gradually assumes its permanent 

 form ; the epididymis appears in the tenth week ; and the gubernaculum (a 

 membranous process from the filamentous tissue of the scrotum, analogous 

 to the round ligament arising from the labium and attached to the ovary 

 in the female), which is originally attached to the vas deferens, gradually 

 fixes itself to the lower end of the testis or epididymis. The Wolffian duct 

 remains as the vas deferens of the male. The Testes begin to descend at 

 about the middle period of pregnancy ; at the seventh month they reach the 

 inner ring; in the eighth they enter the passage; and in the ninth they 

 usually descend into the scrotum. The cause of this descent is not very 

 clear: it can scarcely be due merely, as some have supposed, to the contrac- 

 tion of the gubernaculum ; since that does not contain any fibrous structure 

 until after the lowering of the testes has commenced. It is well known that 

 the testes are not always found in the scrotum at the time of birth, even at 

 the full period. Upon an examination of 97 new-born infants, Wrisberg 

 found both testes in the scrotum in 67, one or both in the canal in 17, in 8 

 one testis in the abdomen, and in 3 both testes within the cavity. Sometimes 

 one or both testes remain in the abdomen during the whole of life ; but this 

 circumstance does not seem to impair their function. 1 This condition is 

 natural, indeed, in the Ram. The Ovary undergoes much less alteration, 

 either in its intimate structure, or in its position. Its efferent canal (which, 

 as just stated, is not the representative of the vas deferens of the male, but 

 is the duct of Miiller) remains detached from it, presents a free terminal 

 aperture, and constitutes the Fallopian tube. The Uterus (which was for- 

 merly supposed to be formed by the coalescence of the Fallopian tubes), is 

 now known to be derived, like the Vagina, from the genital portion of the 

 " uro-genital sinus" ( 789 \ which is formed exactly on the same plan in both 

 sexes alike, at an early period of fu-tal development, and receives at its 

 upper extremity the termination of the Fallopian tubes. In the Female, 

 this canal increases in size, and a marked separation is established between 

 its lower or vaginal portion and its upper or uterine portion. The former 

 opens into the undivided portion of the uro-genital sinus, which also receives 



1 A case oe,eurre<l within tin- Author's knowledge, in which both testes.reimiined 

 in the abdomen until the tenth year, and then descended. 



