996 



DEVELOPMENT OF THE GENERATIVE ORGANS. 



placed on the inner border of the Wolffian bodies. At first, they are placed near to 

 one another, and parallel ; the Wolffian bodies being at that time large, and occu- 

 pying the whole posterior part of the abdomen. But as the kidneys grow, above and 

 internal to the Wolffian bodies, the latter are displaced outwards, and with them the 

 reproductive organs. At this time the sex becomes distinguishable; for in the 

 female the ovary becomes elongated and flattened, and it assumes at first an oblique 

 and then a nearly transverse direction; whereas, in the male, the testis becomes 



Fig. 692. 



Fig. 692. DIAGRAM OP THE 

 PRIMITIVE URINARY AND SEX- 

 UAL ORGANS IN THE EMBRYO 

 PREVIOUS TO SEXUAL DIS- 

 TINCTION. 



The parts are shown chiefly in 

 profile ; the kidney and supra- 

 renal body of the right side are 

 omitted, and the Miillerian and 

 Wolffian ducts are shown from 

 the front. 1, left kidney ; 2, 

 suprarenal body ; 3, ureter ; 4, 

 urinary bladder ; 5, urachus ; 

 ot, the mass of blastema from 

 which ovary or testicle is after- 

 wards formed ; W, left Wolffian 

 body ; x , part at the apex from 

 which the coni vasculosi are 

 afterwards developed in new 

 blastema ; w, iv, right and left 

 Wolffian ducts ; m, m, right and 

 left Miillerian ducts uniting toge- 

 ther and with the Wolffian ducts 

 in g c, the genital cord ; ug, sinus 

 uro-genitalis ; i, lower part of 

 the intestine ; c, I, common open- 

 ing of the intestine and uroge- 

 nital sinus ; c/>, elevation which 

 becomes clitoris or penis ; I s, 

 ridge from which the labia 

 majora or scrotum is formed. 



rounder and thick, and, to- 

 gether with the Wolffian body, 

 retains its vertical position, 

 although displaced downwards 



and outwards. Subsequently the tubuli seminiferi are developed within the testis, 

 and ova in the superficial strata of the ovary. 



Uterus and Fallopian tubes: Epididymis and Vasa deferentia. The excretory 

 duct of each Wolffian body lies from the first along its outer border, and in the 

 succeeding part of its course is continued down from the extremity of the Wolffian 

 body to the sinus urogenitalis. As the Wolffian body begins to change its position, 

 and at the same time decrease in size, a white thread of blastema appears on the 

 front of that body, and runs along the inner side of the Wolffian duct in its whole 

 course ; this fcrms the Mullerian duct. At the upper extremity of the Wolffian body, 

 and close to the white thread, there is likewise developed a pyramidal mass of blas- 

 tema, occupying the position originally held by the upper tubules of that gland, 

 which seem to be absorbed to give place to it. The Mullerian duct, commencing by a 

 slightly dilated extremity, descends in front of the excretory duct, to the lower end 

 of the Wolffian body, where it dips down in front of that body, then turns over that 

 duct so as to get behind it, and on arriving at the middle line comes in contact with 

 its fellow of the opposite side, with which, and with the lower parts of the Wolffian 

 ducts, it is united into a single cord, named the genital cord. The Mullerian ducts 

 become as it were fused together, first at the upper and lower parts of the genital 



