BRANCHES OF THE INTERNAL ILIAC ARTERY. 809 
In the first part of its course in the perineum the artery lies in the outer 
fascial wall of the ischio-rectal fossa, where it is enclosed in the space known as 
Aleock’s canal. This, which is situated about one and a half inches above the lower 
margin of the tuberosity of the ischium, contains also the pudic veins and the 
terminal parts of the pudie nerve, viz. the dorsal nerve of the penis which lies 
above the artery, and the perineal division which hes below the vessel. From the 
ischio-rectal fossa the internal pudic is continued forwards between the two layers 
of the triangular ligament of the urethra, and close to the ramus of the pubis. 
About half-an-inch below the sub- pubic lgament it turns somewhat abruptly 
forwards, pierces the anterior layer of the triangular ligament, and immediately 
divides into its terminal branches, viz. the artery of the corpus cavernosum and 
the dorsal artery of the penis. The division sometimes takes place whilst the 
artery is still between the layers of the triangular ligament. 
Branches.—/n the pelvis it gives small branches to the neighbouring muscles and to 
the roots of the sacral plexus. 
In the buttock.—(a) Muscular branches are given to the adjacent muscles. 
(4) Anastomotic branches unite with branches of the gluteal sciatic and internal 
circumflex arteries. 
In the ischio-rectal fossa.—(c) The inferior hemorrhoidal artery (a. hemorrhoidalis 
inferior) pierces the inner wall of Alcock’s canal, and runs obliquely forwards and 
inwards. It soon divides into two or three main branches, which, sometimes arising 
separately, pass across the space to the lower part of the rectum. The artery anasto- 
moses in the walls of the rectum with its fellow of the opposite side, and with the middle 
and superior hemorrhoidal arteries ; it also anastomoses with the transverse perineal 
arteries, and it supplies cutaneous twigs to the region of the anus, and others which turn 
round the lower border of the gluteus maximus to supply the lower part of the 
buttock. 
(d) The superficial perineal artery (a. perinei) arises in the anterior part of the ischio- 
rectal fossa, pierces the base of the triangular ligament, and divides into long slender 
branches (aa. scrotales posteriores in the male, labiales posteriores in the female) which 
are continued forwards in the urethral triangle, beneath the superficial perineal fascia, 
to the scrotum. It anastomoses with its fellow of the opposite side, with the transverse 
perineal and the external pudic arteries, and it supplies the muscles and subcutaneous 
structures of the urethral triangle. 
(ec) The transverse perineal artery is a small branch which arises either from the internal 
pudie or from its superficial perineal branch. It runs inwards along the base of the 
triangular ligament to the central point of the perineum, where it anastomoses with its 
fellow of the opposite side, with the superficial perineal branch, and with the inferior 
hemorrhoidal arteries. It supplies the sphincter ani, the bulbo-cavernosus or sphincter 
vaginee, and the anterior fibres of the levator ani. 
In the urethral triangle.—(f) The artery to the bulb (a. bulbi urethra), a brauch 
which is usually of relatively large size, is given off between the layers of the triangular 
ligament. It runs transversely inwards along the posterior border of the compressor 
urethre, and then turning forw ‘ards a short distance from the outer side of the urethra, 
it pierces the anterior layer of the triangular ligament and enters the substance of the 
bulb. It passes onwards in the cor pus spongiosum to the glans, where it anastomoses 
with its fellow and with the dorsal arteries of the penis. 
It supplies the compressor urethree muscle, Cowper’s- gland, the corpus spongiosum, 
and the penile part of the urethra. In the female this artery supplies the bulb of the 
vestibule. 
(7) The artery of the corpus cavernosum (a. profunda penis in the male; a. pro- 
funda clitoridis in the female) is usually the larger of the two terminal branches. 
Immediately after its origin it enters the crus penis, and runs forwards in the corpus 
cavernosum, which it supplies. 
(kh) The dorsal artery of the penis (a. dorsalis penis in the male ; a. dorsalis clitoridis 
in the female) passes forwards between the layers of the suspensory ligament, and runs 
along the dorsal surface of the penis with the dorsal nerve immediately to its outer side, 
whilst it is separated from its fellow of the opposite side by the single dorsal vein. It 
supplies the superficial tissues on the dorsal aspect of the penis, sends branches into the 
corpus cavernosum to anastomose with the artery to the corpus cavernosum, and its terminal 
branches enter the glans penis, where they anastomose with the arteries to the bulb. It 
also anastomoses with the external pudic branches of the femoral. 
