1058 URIXARV AXD REPRODUCTIVE ORGANS 



while the genital eminence ceases to enlarge and remains as the clitoris. In the male the evolu- 

 tionary processes go farther. The margins of the uro-genital sinus fuse in the middle line to close 

 in a prolongation of the urethra on the ventral aspect of the genital eminence and to form the 

 scrotum, the i)rocess being concluded about the fitteenth week ; finally, a jujuch of jieritoneum 

 makes its way on each side through the abdonjinal wall into the corresi)onding half of the scro- 

 tum, and into this the testicle ultimately descends, guided by the gubernaculum (page 1025). 

 The glands of Cowper or Bartholin in both .sexes are formed by involutions of ei)ithelium near 

 the root of the rudimentary clitoris or i)enis. 



Should the process of mesial fusion lail, the urethra may present a fistulous opening on its 

 ventral side, or may remain cleft from the meatus upwards for a greater or less distance. In the 

 more aggravated forms the defect of union involves the scrotum also, and leads to a s]>urious 

 liermaphrodism in which is perpetuated a superficial resemblance to the female genitals, the sim- 

 ulation being made greater by the imperfect descent of the testicles. All these congenital defects 

 are clearly accounteil for by ascertained facts in morphology ; but there is a malformation which 

 our present knowledge does not satisfactorily explain — that known as 'extroversion of the blad- 

 der,' in which a non-closure of the ventral parietes below the umbilicus coincides with a fis.sure 

 in the anterior wall of the allantoic bladder, and leads to an extrusion of the posterior wall of the 

 viscus. Mr. Shattock suggests that the condition is perhaps the result of an undue extension 

 forwards of the cloacal fissure ; but the problem cannot yet be regarded as solved. 



TRF PERINEUM 



The term perinaeum {T^spi, '^alm) has been variously applied Vjy anatomists — 

 firstly, in its original and general meaning, to the soft parts connected with the 

 pelvic outlet; secondly, to the anterior or genito-urinary segment only of these 

 parts; and thirdly, to the tissues separating the vulvo-vaginal and ano-rectal 

 passages. It is here employed in the first and broader sense, the expression 

 ' perineum proper ' being used for the second application, and that of ' perinatal 

 body ' for the third. 



The outlet of the pelvis is a lozenge-shaped space bounded in front by the 

 symphysis and subpubic ligament, behind by the tip of the coccyx, and on each 

 side by the conjoined rami of os pubis and ischium, the tuber ischii, and the inferior 

 border of the great sacro-sciatic ligament. The latter structure is overlapj^ed to a 

 variable extent by the gluteus maximus, which also covers the tuber ischii when 

 the thighs are extended; but the glutei are merely accessory to the true boundaries. 



The dimensions of the outlet in the male and female are given on page 146. 

 The further anatomy of the parts differs in the two sexes. 



THE MALE PERINyEUM 



The integument of the perinaeum is pigmented, beset with scattered hairs, 

 and provided with large sebaceous and sudoriparous glands. Its deeper layers 

 contain an abundance of smooth muscular fibre continuous with the dartos of the 

 scrotum, and these are so disposed around the anal margin as to corrugate the 

 skin into radiating folds during their contraction. 



The landmarks of the region are for the most part well-defined. Tlio symphysis 

 in front is obscured by the root of the penis, which may be traced backwards as a 

 soft median prominence as far as a point an inch anterior to the anus. On each 

 side the pubic and ischial rami may be felt running outAvards and l)ackwards to 

 expand into the ischial tuberosity, which is uncovered by the gluteus maximus 

 when the thigh is flexed. Extending backwards and inwards from the tuberosity 

 may be detected, in thin subjects, the resistance of the great sacro-sciatic ligament; 

 and still more posteriorly the coccyx is felt in the middle line immediately beneath 

 the skin. The anal ajierture, surrounded by radiating furrows, lies a short distance 

 in front of the coccyx, and on ench side of it is a depression called the ischio- rectal 

 fossa, the superficial aspect of which depends upon the amount of fat which occu- 

 pies it. 



