PERINEUM. 



933 



the operator's success in lithotomy turns upon 

 his knowledge of the relations, the size, and 

 the density of this organ as well as of the re- 

 sistance of its capsule. The prostate is heart- 

 shaped; it has been also not unaptly compared 

 to a chesnut. Its base, directed backwards 

 and upwards, embraces the neck of the bladder, 

 and usually presents a notch for the entrance 

 of the ejaculatory ducts; its apex, truncated 

 and directed forwards and downwards, is in 

 contact with Wilson's muscles and separated 

 from the triangular ligament of the urethra by 

 an interval of less than half an inch; its under 

 surface, grooved longitudinally in the middle 

 line, looks somewhat backwards and rests upon 

 the rectum with the intervention of a quantity 

 of rather dense cellular tissue, in which fat 

 never accumulates ; its upper surface, inclining 

 slightly forwards and less extensive than the 

 lower, is connected to the pubis by the anterior 

 true ligaments of the bladder ; and its sides, 

 winch are rounded, are covered by the levatores 

 ani muscles. The vesiculse seminales are re- 

 lated to the base of the prostate gland, and the 

 dorsal veins of the penis lie upon its upper 

 surface, which is scarcely three-quarters of an 

 inch distant from the pubis. The rectum, when 

 empty, is in contact with the under surface 

 only of the prostate, but when distended, it 

 also encroaches upon the sides of the gland ; 

 this occurs to an extreme degree whenever the 

 bowel presents the dilatation so commonly 

 observed in elderly persons ; in such cases the 

 prostate appears embedded in the walls of the 

 gut, a disposition fraught with danger to the 

 intestine in the ordinary operation for stone. 



The prostate gland varies so much in size at 

 different periods of life, and even in different 

 individuals of the same age, that it is impossi- 

 ble to specify its exact dimensions. The organ 

 is small in the child ; it increases greatly at 

 puberty; in middle age its measurements are 

 still larger, and in the decline of life they 

 become not unfrequently excessive. In the 

 healthy adult subject, the extreme length of the 

 prostate gland from base to apex may be esti- 

 mated at from an inch and a quarter to an inch 

 and a half; its depth at the base seldom ex- 

 ceeds one inch, whilst from side to side it 

 measures somewhat more than an inch and a 

 quarter. The urethra traverses the prostate from 

 base to apex, and runs much nearer to the upper 

 than to the lower surface of that body, so that the 

 canal is very unequally surrounded by glandu- 

 lar substance. At the base of the prostate the 

 glandular substance above the urethra varies 

 from two to four lines in depth ; below the 

 canal it is upwards of six lines deep; laterally 

 its thickness may be estimated at about eight 

 lines, whilst in the direction of the ordinary 

 incision in lithotomy, viz. downwards and out- 

 wards, from nine to twelve lines is the average 

 measurement. Exceptional cases have been 

 reported by Velpeau and others, in some of 

 which no trace of glandular substance existed 

 above the urethra, and in others little or none 

 beneath it; the latter variety might lead to un- 

 pleasant consequences in lithotomy. 



The prostate gland is enveloped by a dense 



capsule continuous with the fibrous membrane 

 derived from the posterior layer of the triangu- 

 lar ligament of the urethra, and investing the 

 membranous portion of that canal. This cap- 

 sule is identified above with the anterior and 

 lateral true ligaments of the bladder, and its 

 strength is such as to impart great firmness to 

 the prostate, and a power of resistance altoge- 

 gether foreign to the glandular substance. The 

 anatomist finds it extremely difficult to lacerate 

 the prostate so long as the capsule retains its 

 integrity, but a trifling force suffices to tear or 

 to split the gland after it has been deprived of 

 this covering. The strength of the capsule 

 explains the difficulty experienced by lithoto- 

 mists in dividing the prostate gland by the 

 cutting gorget, and was doubtless in great 

 measure the cause of those distressing accidents 

 which so frequently resulted from the slipping 

 of that instrument, and which have led to its 

 disuse in latter years. The common ejacula- 

 tory ducts traverse the prostate gland from 

 behind forwards and upwards ; they are closely 

 approximated to each other, and for practical 

 purposes may be considered to occupy the 

 middle line. It would be impossible to 

 effect with certainty a median section of the 

 gland in the living subject without injury to 

 one or both of these ducts: this constitutes a 

 strong objection to the recto-vesical operation 

 of lithotomy, but they are out of danger in the 

 lateral and bilateral methods. 



The veins in the neighbourhood of the pros- 

 tate gland and of the neck of the bladder are 

 remarkable for their plexiform arrangement, 

 and are called the vesico-prostatic plexus. This 

 plexus, receiving anteriorly the dorsal veins of 

 the penis after their entrance into the pelvis, 

 and communicating posteriorly witli the he- 

 morrhoidal veins, delivers its blood into the 

 internal iliacs; it lies chiefly upon the upper 

 and lateral surfaces of the prostate, and on the 

 lateral and inferior aspects of the neck and 

 neighbouring portion of the base of the blad- 

 der. The veins which constitute this plexus 

 are covered by a layer of the capsule of the 

 prostate, and bound down to the bladder by a 

 strong membrane derived from the recto-vesical 

 lamina of tlie pelvic fascia. They communi- 

 cate in the freest manner with each other, and 

 are but moderately developed in young and 

 healthy subjects, whilst in elderly persons and 

 in cases of chronic disease of the bladder, as 

 well as in calculous affections, they occasionally 

 attain to an immense size and assume a vari- 

 cose disposition. The hemorrhage from ves- 

 sels so enlarged might be followed by a fatal 

 result in lithotomy. The mouths of these veins 

 remain permanently patent after they are di- 

 vided ; this results from the fibrous investment 

 which binds them down, and has been supposed 

 by the French surgeons to predispose them to 

 phlebitis after operations, by exposing their 

 delicate lining membrane to the irritating influ- 

 ence of the urinary stream. 



An irregular artery is sometimes found along 

 the side of the prostate gland, and has been 

 the source of fatal hemorrhage when divided 

 by the lithotomist. This vessel is destined to 



