STRUCTURE OF EJACULATORY DUCTS AND PROSTATE GLAND. 295 



epithelium of the ducts, as it approximates the vesicula 

 prostatica, quickly begins to assume the transitional form, 

 presenting a superficial layer of short cylindrical or club- 

 shaped cells, and a deep one of smaller almost polyhedric or 

 bub little elongated cells. At the openings of the ducts the 

 laminated pavement epithelium of the vesicula prostatica is 

 continued for a short distance into their interior. The surface 

 of the mucous membrane is here also irregular, presenting 

 longitudinal and transverse rugae, which increase in number 

 and size towards the opening of the ducts. The mucous mem- 

 brane is 0'06 of a millimeter in thickness, and is composed of 

 connective tissue arranged in the form of a plexus, the fibres 

 of which for the most part run parallel to the axis of the tube, 

 and are accompanied by some longitudinal fasciculi of smooth 

 muscular tissue. Outside the mucous membrane is a circular 

 layer of muscular tissue, having a thickness of 0' 6 6 of a milli- 

 meter which is prolonged beyond the ductus ejaculatorii into 

 the circular muscular layer of the vesicula prostatica to be 

 presently described. 



IV. PROSTATE. The structure of the prostate presents two 

 distinct constituents gland substance and muscular tissue. 

 The latter, as Kolliker has shown, constitutes the proper stroma 

 of the prostate, whilst the connective tissue only forms very 

 thin trabeculse, representing the septa of the muscles and the 

 supporting material for the vessels and nerves that penetrate 

 from without into the substance of the organ. The prostate 

 is invested externally by a sheath of connective tissue that is 

 directly continuous with the tendons of the smooth muscular 

 bands in immediate contact with it. These last run either 

 circularly or obliquely, with a few longitudinal fasciculi inter- 

 spersed amongst them, and collectively form the proper cortical 

 substance of the prostate. From the cortical muscular layer 

 strong bands of smooth muscular fibres run towards the centre, 

 decussating freely in their course, and forming meshes in which 

 the gland substance is imbedded. The thickness of the muscular 

 cortex is different in that portion of the organ which is in 

 front of the urethra from that which lies behind it ; and in 

 the latter again it differs in its upper, middle, and lower parts ; 



