PERIN.EAL ARTERY AND NERVES. 393 



The other deeper, but more membranous part, is of limited extent, and 

 is connected with the firm subjacent structures. Externally it is fixed to 

 the pubic arch of the hip-bone, outside the line of the crus penis and its 

 muscle, extending as low as the ischial tuberosity. Posteriorly the stratum 

 bends down to join the triangular ligament of the urethra ; but in front it 

 is unattached, and is continued to the scrotum and penis. By means of 

 similar connections of the membrane on both sides, a space is enclosed 

 over the anterior half of the perinaeum. From its under surface a septum 

 dips downwards in the middle line, and divides posteriorly the subjacent 

 space into two ; but anteriorly this partition is less perfect, or may disap- 

 pear. 



Air blown beneath the fascia passes forwards to the scrotum ; and this 

 direction is given to it by the deep connections of that membrane with 

 parts around. Should urine be effused beneath the superficial fascia, the 

 fluid will necessarily be directed forwards, like the air, through the scrotum 

 to the penis and the front of the abdomen. 



Dissection. The superficial vessels and nerves are to be dissected on the 

 right side of the perinaeum, by cutting through the superficial fascia in tho. 

 same manner as on the left side. The long slender artery then visible is 

 the superficial perinatal, which gives a transverse branch near its com- 

 mencement. Two superficial perinaeal nerves accompany the artery ; and 

 the inferior pudendal nerve is to be traced forwards to the scrotum. Com- 

 munications are to be sought between these nerves anteriorly, and between 

 one of the perinatal and the inferior hsemorrhoidal posteriorly ; and all the 

 nerves are to be followed backwards. 



ARTERIES (fig. 130). The superficial and transverse perinaeal arteries 

 beneath the fascia are branches of the pudic, and are two or three in 

 number. 



The superficial perinceal branch (fig. 130, i), arising at the fore part 

 of the ischio-rectal fossa, runs over or under the transverse muscle, and 

 beneath the superficial fascia to the back of the scrotum, where it ends in 

 flexuous branches. As the vessel lies internal to the pubic arch, it sup- 

 plies offsets to the muscles beneath ; and in front it anastomoses with the 

 external or superficial pudic branches of the femoral artery. Sometimes 

 there is a second perinaeal branch. 



The transverse artery of the perinaeum (fig. 130, a) arises from the 

 preceding, and is directed transversely to the middle of the perinatal space, 

 where it is distributed to the integuments and the muscles between the 

 urethra and the rectum. It anastomoses with the one of the opposite side. 



Branches of veins accompany the arteries, and open into the trunk of 

 the pudic vein ; those with the superficial perinaeal artery are plexiform at 

 the scrotum. 



NERVES (fig. 130). There are three cutaneous nerves of the scrotum on 

 each side, viz., inferior pudendal of the small sciatic, and two superficial 

 perin,geal branches of the pudic nerve. 



The superficial perinceal nerves, two in number, are named anterior 

 and posterior from their relative position : both arise in the ischio-rectal 

 fossa from the perinaeal branch of the pudic nerve (p. 391). 



The posterior branch ( 2 ) is continued forwards, beneath the superficial 

 fascia, with the artery of the same name to the back of the scrotum. 

 Whilst in the fossa the nerve gives inwards an offset to the integuments 

 in front of the anus ; and this communicates with the inferior haemorrhoidal 

 nerve. 



