230 THE PHYSIOLOGY OF REPRODUCTION 



The coats of the ejaculatory ducts are relatively thin. The 

 lining epithelium is similar to that of the vas deferens. 



The urethra, which serves as the common channel for both 

 urine and seminal fluid, is Uned by a columnar epithehum resting 

 on a vascular corium. The latter is surrounded by submucous 

 tissue containing two layers of muscular fibres, the inner 

 being arranged longitudinally, and the outer circularly. The 





Fig. 55^ — Transveise section through commencement of vas deferens. 

 (After Klein, from Schtifer.) 



a, epithelium ; 6, mucous membrane ; f, d, c, inner, middle, and outer 

 layers of muscular coat ; /, internal cremaster muscle; g, blood-vessel. 



urethra in man is usually described as consisting of three 

 divisions, the prostatic, the membranous, and the spongy 

 portions. Of these the membranous portion comprises that 

 part of the urethra between the apex of the prostate and the 

 bulb of -the corpus spongiosum, to be described below. Opening 

 medially into the prostatic portion of the urethra, between the 

 two ejaculatory ducts, is the aperture of the uterus mascuUnus, 

 or organ of Weber, which is the homologue of the vagina and 



