GENERATION AND DEVELOPMENT. 303 



inguinal canal, from the outer and upper part of the uterus to the subcu- 

 taneous tissue in front of the symphysis pubis. 



At a very early stage of foetal life, the Wolffian ducts, ureters, and 

 Mullerian ducts, open into a receptacle formed by the lower end of the 

 allantois, or rudimentary bladder; and as this communicates with the 

 lower extremity of the intestine, there is for the time a common recep- 

 tacle or cloaca for all these parts, which opens to the exterior of the body 

 through a part corresponding with the future anus, an arrangement 

 which is permanent in Reptiles, Birds, and some of the lower Mammalia. 



FIG. 464. Diagram of the Wolffian bodies, Mullerian ducts and adjacent parts previous to sexual 

 distinction, as seen from before, s r, the supra-renal bodies; r, the kidneys; o t, common blastema 

 of ovaries or testicles; W, Wolffian bodies; w. Wolffian ducts; m, m, Mullerian ducts; g c, genital 

 cord; u g, sinus urogenitalis ; i, intestine; c Z, cloaca. (Allen Thomson.) 



In the human foetus, however, the intestinal portion of the cloaca is cut 

 off from that which belongs to the urinary and generative organs; a sepa- 

 rate passage or canal to the exterior of the body, belonging to these parts, 

 being called the sinus urogenitalis. Subsequently, this canal is divided, 

 by a process of division extending from before backward or from above 

 downward, into a "pars urinaria" and a "pars genitalis." The former, 

 continuous with the uraclms, is converted into the urinary bladder. 



The Fallopian tubes, the uterus, and the vagina are developed from 

 the Mullerian ducts (Fig. 464, m, and Fig. 465) whose first appearance 

 has been already described. The two Mullerian ducts are united below 

 into a single cord, called the genital cord, and from this are developed 



