330 HISTOLOGY 



the Wolffian duct is arbitrarily divided in the adult into three parts, the 

 ductus epididymidis, ductus deferens, and ductus ejaculatorius. 



It has been noted that only 10-15 f the Wolffian tubules persist as 

 efferent ducts; in man, according to Felix, these are the fifty-eighth to 

 seventieth out of a series of eighty-three which develop. Thus a great 

 many degenerate, and certain appendages of the epididymis are explained 

 as persistent remnants. The appendix epididymidis may represent a 

 part of the Wolffian duct or an anterior tubule (Fig. 328); its history 

 is still obscure. Other anterior tubules may be retained as appendages 

 of the rete. The paradidymis is "a functionless remnant of the Wolffian 

 body," situated behind the head or upper end of the epididymis and in 

 front of the cord of veins which accompany the ductus deferens. 



Giraldes first described it (Bull. Soc. Anat. Paris, 1857) and Koelliker named it the 

 "organ of Giraldes"; Henle called it the paraepididymis (i.e., the organ beside the epi- 

 didymis), and Waldeyer later shortened the term and changed its meaning. Felix 

 (loc. cit., 1912) contrary to the earlier descriptions, places the paradidymis "between 

 the epididymis and the testis, slightly below the head of the epididymis." Toldt 

 (Verb. Anat. Gesellsch, 1892, pp. 241-242) recognized two forms of paradidymis, but 

 both are behind the epididymis and in front of the veins of the spermatic cord. The 

 precise origin of these tubules from the Wolffian body has not been determined. 



Other remains of the Wolffian body, apparently derived from the 

 tubules below those which become efferent ducts, are known as aberrant 

 ducts (ductuli aberr antes}. There may be two or three of them; usually 

 there is said to be but one. It proceeds from the duct of the epididymis, 

 or rarely from the ductus deferens at its junction with the duct of the 

 epididymis, and terminates in a coiled mass, sometimes having branches. 

 The length of the aberrant duct is "4-36 cm., generally 5-8 cm." (Henle). 



The External Genital Organs. After the cloaca has been divided into 

 ventral and dorsal portions by the downward growth of the perineal sep- 

 tum, the ventral portion below the outlets of the Wolffian ducts is called 

 the urogenital sinus. It receives both urinary and genital products, and 

 in the male it forms all of the urethra below the orifices of the ejaculatory 

 ducts. In the young embryo, the distal part of the urogenital sinus be- 

 comes laterally compressed so that it forms an epithelial plate. This 

 plate reaches the external surface of the body along the mid-ventral line 

 of an elevation known as the genital papilla (or tubercle). The genital 

 papilla (Fig. 326) becomes very prominent in embryos of both sexes. In 

 the male it continues its development and forms the penis, along the under 

 side of which the urogenital sinus acquires a cleft-like opening (Fig. 329, 

 A). This elongated aperture closes from behind forward, along the line 

 permanently marked by a rap he (or seam). In the abnormal cases of 

 hypospadias, the urogenital sinus retains a more or less extensive opening 

 on the under side of the penis. A rounded terminal glans is early differen- 



