THE PROSTATE. 



449 



ejaculatory ducts. These enter close together near the median line and pass upward 

 and forward to enter the under surface of the prostatic urethra about its middle. It 

 is to the part of the prostatic tissue between the ejaculatory ducts below and the 

 interior of the bladder above, just posterior to the urethral orifice, that the name 

 middle lobe has been applied. This part contains a collection of glands called by 

 Albarran (Albarran and Motz: Annales dcs Mai. Genito-Urinaires, July, 1902) the 

 prespermatic group. Just beneath the mucosa behind the urethra is another group 

 which he calls the subcervical group. In so-called enlargements of the middle lobe 

 these glands form the bulk of the tissue. A slight enlargement produces a bar, a 

 considerable enlargement produces a projecting growth which may even be peduncu- 

 lated. The glandular portion of the prostate in addition to that just described pos- 

 terior to the urethral orifice is located centrally, and the fibromuscular part of the 

 gland is mostly outside of the glandular portion, surrounding it and passing across 



Prostatic veins 



Deep layer tri- 

 angular ligament 



Superficial layer 

 triangular ligament 



Rectovesical fascia 



^ Layer covering 

 """seminal vesicles 

 Layer covering 

 the rectum 



Internal sphincter 

 Sheath of prostate 

 Capsule of prostate 

 Separable space 

 Rectal layer of fascia 



Recto-urethralis 

 muscle 



Deep transverse 

 perinea! muscle 



Internal sphincter 

 Cowper's gland 



^External sphincter 



Superficial transverse 

 perineal muscle 



Membranous urethra 

 FIG. 454. The prostate and its fascias. 



the median line in front of the urethra to form the anterior commissure. Some fibres 

 cross the median line posteriorly, forming an indistinct posterior commissure. 



Sheath and Capsule. The prostate is surrounded by a distinct firm fibrous 

 sheath which is continuous with the rectovesical fascia (aponeurosis of Denon- 

 villiers). At the upper portion this blends with the fascia covering the bladder, 

 anteriorly it forms the puboprostatic ligaments, below it is continuous with the deep 

 layer of the triangular ligament of the perineum, posteriorly it is continuous with 

 the rectovesical fascia and covers and binds the seminal vesicles to the bladder. 

 The prostatic plexus of veins is imbedded in this fibrous sheath. (J. W. Thomson 

 Walker, Brit. Med. Jour., July 9, 1904.) (Fig. 454). 



Between the veins and the glandular tissue, and covering the latter, is what has 

 been called by Sir Henry Thompson and W. G. Richardson ( ' ' Development and 

 Anatomy of the Prostate Gland ") the capsule. It is a comparatively thin layer of 

 fibrous tissue, insignificant and incomplete in places, which penetrates the substance 

 of the gland. It adheres to and is removed with the lobes of the enlarged prostate 

 in prostatectomy. 



C. S. Wallace {Brit. Med. Jour., 1904, i., p. 239) holds that what Sir H. Thompson 

 has called the capsule is the thin, muscular, outer, nonglandular portion of the organ. 

 29 



