1122 



SURGICAL AXD TOPOGRAPHICAL ANATOMY 



Collateral circulation after ligature of the external iliac :- 



Deep epigastric 



with 



Internal mammary, lower inter- 



costals, and lumbar. 

 Ilio-lumbar, lumbar, and gluteal. 

 Internal and external circumflex. 

 Perforating branches of profunda. 

 Circumflex and epigastric. 

 External pudic. 



Branches of profunda. 

 Inferior mesenteric. 

 Vessel of opposite side. 

 Branches of opposite side. 



Sciatic and gluteal. 



Middle sacral. 

 Ilio-lumbar and gluteal. 



TRF PERIN^U3I AND GENITALS 



Bony boundaries. — These are the same in either sex. Al)ove and in front is 

 the symphysis pubis, rounded off by the subpubic ligament ; diverging downwards 

 and outwards from this point on either side are the rami of the pubes and ischium, 

 ending at the tuberosities of the latter. In the middle line behind is the apex of 

 the coccyx; and reaching from this to the tuberosities are the great sacro-sciatic 

 ligaments, to be felt by deep pressure, with the lower border of the gluteus 

 maximus overlapping them. The depth of the peringeum varies greatly, from 

 two to three inches (30 to 75 mm.) in the posterior and outer part to one inch or 

 less in front. 



In the middle line, extending longitudinally through the perinseum, is the 

 raphe, the guide to the urethra, and ' the line of safety ' (on account of the small 

 size of the vessels here) for operations on it. 



An imaginary line drawn transversely across the ^^crina'um from one tul)er ischii 

 'to its fellow divides the lozenge-shaped space into two triangles — (1 ) An anterior, 

 or urethral ; and (2) a posterior, or rectal. 



The central point of the perinaeum is in the adult nearly an inch (25 mm. ) in 

 front of the anus, or midway between the centre of the anus and root of the scrotum. 

 Here the following structures meet, viz., the sphincter ani, the two transverse peri- 

 natal muscles, the accelerator urinse, and the levator ani. It also corresponds to the 

 centre of the loAver margin or base of the triangular ligament. Its development 

 varies much in different bodies. A little in front of this point is the bulb, with the 

 corpus spongiosum })assing forwards from it. This would also be the level of the 

 artery of the l)ulb, so that in lithotomy the incision should always begin below 

 this point. A knife introduced at the central ])oint, and carrietl backwards and 



