266 HISTOLOGY. 



measures about 20 feet when straight (6-7 meters). Together with the 

 efferent ducts this coiled mass constitutes the epididymis. Along the testis 

 the Wolffian duct is called the ductus epididymidis and from the testis 

 toward the urogenital sinus it is named the ductus deferens. Near its 

 termination a saccular outgrowth, like a distended gland, develops from 

 each Wolffian duct. It is called the seminal vesicle, and that portion of 

 the Wolffian duct between the duct of the vesicle and the urethra is named 

 the ejaculatory duct. Thus the Wolffian duct is arbitrarily divided in 

 the adult into three parts, the ductus epididymidis, ductus deferens, and 

 ductus ejaculatorius; an out-pocketing forms the seminal vesicle. 



It has been noted that only about fifteen of the Wolffian tubules 

 persist as efferent ducts. Some of the others become detached, producing 

 the paradidymis; and some which are partly detached remain as blind 

 tubes extending from the rete or ductus epididymidis, they are called 

 ductus aberrantes. The one of these labelled in Fig. 301 is quite constant 

 and may be from 5 to 30 cms. in length. The appendix epididymidis in 

 the figure contains a tube connected with the Wolffian duct. The nature 

 of this appendix is obscure; it has been thought a derivative of the Miil- 

 lerian duct. 



The urethra. At an early stage (Fig. 299) the allantois is arbitrarily 

 divisible into a 'temporary bladder' which extends to the genital ducts, and 

 a urogenital sinus which receives both urinary and sexual outlets and 

 extends to the surface of the body. A portion of the urogenital sinus is 

 ectodermal having formed from a depression in the outer surface; its inner 

 part is entodermal and the boundary between these portions is no longer 

 apparent. At a later stage the 'temporary bladder' forms the permanent 

 bladder together with a limited portion of the urethra. In the female 

 it forms the entire urethra, but in the male only that portion of the pros- 

 tatic urethra which extends to the genital ducts. The remainder of the 

 male urethra is urogenital sinus. By the anatomists the male urethra 

 is divided into the prostatic, membranous and cavernous [penile] portions. 



The penis and scrotum. In Fig. 299 the outer portion of the uro- 

 genital sinus is seen to be a cleft-like space in an elevation known as the 

 genital papilla (or tubercle). In Fig. 302, A, the papilla has lengthened 

 to form the penis; its enlarged distal end is the glans. On the lower sur- 

 face of the penis the urogenital sinus has an elongated opening. Apart 

 from the condition of arrested development called hypospadias, the open- 

 ing is bridged over, except at its distal end; thus it forms the cavernous 

 part of the urethra. The embryonic penis is covered with a layer of skin 

 described as forming two lateral folds, the lesser genital folds. They meet 

 beneath the penis as the urogenital sinus becomes closed, and a raphe 



