FASCLE OF THE PEKINEUM. 485 



micturition, parturition, and laboured expiration. (2) They are also flexors of the vertebral 

 column and pelvis the muscles of both sides acting together ; the vertebral column and pelvis 

 are laterally flexed, when one set of muscles acts alone. 



The posterior muscles of the abdominal wall and pelvis major include the 

 psoas (major and minor) and iliacus, described already (p. 410), and the quadratus 

 lumborum. 



M. Quadratus Lumborum. The quadratus lumborum lies in the posterior 

 wall of the abdomen, lateral to the psoas, and extends between the iliac crest and 

 the last rib. It arises from the posterior part of the iliac crest, from the ilio- 

 lumbar ligament, and from the transverse processes of the lower lumbar vertebrae. 



It is inserted, above, into the medial part of the inferior border of the last rib 

 and the transverse processes of the lumbar vertebrae. Its lateral border is directed 

 obliquely upwards and medially. 



It is enclosed between the anterior and middle layers of the lumbo-dorsal 

 aponeurosis (p. 437^ between the psoas major muscle, in front, and the sacro- 

 spinalis behind. 



Nerve-Supply. The quadratus lumborum is supplied directly by branches from the anterior 

 rami of the first three or four lumbar nerves. 



Actions. The muscle is a lateral flexor of the vertebral column, an extensor of the column 

 and a muscle of inspiration. 





FASCIAE AND MUSCLES OF THE PERINEUM 



AND PELVIS. 



FASCIAE OF THE PERINEUM. 



The superficial fascia of the perineum possesses certain special features. It 

 is continuous with the superficial fascia of the abdominal wall, thigh, and buttock, 

 and is prolonged on to the penis and scrotum. In the penis, it is devoid of fat 

 and consists only of areolar tissue. In the scrotum, it is intermingled with in- 

 voluntary muscular fibres, and constitutes the dartos muscle, which assists in 

 suspending the testes and corrugating the skin of the scrotum. This fascia 

 also forms the septum of the scrotum, which, extending upwards, incompletely 

 separates the two testes and their coverings. In the female the superficial 

 fascia, in which there is a considerable quantity of fat, takes a large share in 

 the formation of the mons Veneris and labia majora pudendi. 



The fascia over the posterior part of the perineum fills up the ischio-rectal fossae, 

 in the form of two pads of adipose tissue, on either side of the rectum and anal 

 canal. Over the tuberosities of the ischium the fat is intermingled with bands of 

 fibrous tissue closely adherent to the subjacent deep fascia. 



The fascia in the anterior part of the perineum closely resembles the same 

 fascia in the groin. It is divisible into a superficial fatty and a deeper membranous 

 layer ; the former continuous with the same layer in the thigh, and with the fat 

 of the ischio-rectal fossa posteriorly. The deeper membranous layer is attached 

 laterally to the pubic arch, posteriorly to the base of the fascia inferior of the 

 urogenital diaphragm and in the median plane to the root of the penis (bulb 

 and corpus cavernosum urethra) by a median raphe continuous, farther forwards, with 

 the septum of the scrotum mentioned above. Anteriorly the fascia is continued 

 over the spermatic funiculi to the anterior abdominal wall. The importance of 

 this fascia lies in relation to the extravasation of urine from a rupture of the 

 urethra in the perineum. By the fascial attachments the fluid is prevented from 

 ; passing posteriorly into the ischio-rectal fossa, or laterally into the thigh. It is 

 directed forwards into relation with the scrotum and penis, and along the 

 spermatic funiculus to the anterior abdominal wall. The septum of the scrotum 

 being incomplete, fluid extravasated on one side can pass across the median plane 

 1 to the opposite half of the perineum and scrotum. 



The deep fascia of the perineum exists only in the form of the delicate 

 fasciae of the muscles. 



