1038 



SURGICAL ANATOMY OF THE PERIOEUM. 



sufficiently described (p. 97). The anterior portion of the space, which is 

 appropriated to the urethra and the penis, is named the perinceum. This 

 part is triangular, the sides being formed by the sides of the pubic arch 

 meeting at the symphysis pubis, while a line extended between the two 

 ischial tuberosities represents the base of the triangle. In well-formed bodies 

 the three sides of the space are equal in length ; but cases occur in which, 

 by the approximation of the ischiatic tuberosities, the base is narrowed ; 

 and we may anticipate the practical application of the anatomical facts so 

 far as to state here, that this circumstance exercises a material influence on 

 the operation of lithotomy, inasmuch as the incisions required in that 

 operation, instead of being oblique in their direction, must, in such circum- 

 stances, be made more nearly straight backwards. 



That portion of the outlet of the pelvis which lies behind the perinseum 

 may be named the ischio-rectal region. It contains the end of the rectum ; 

 and it is defined by the ischial tuberosities, the coccyx, and the great 

 gluteal muscles. We shall now proceed to the detailed examination of the 

 two parts thus mapped out. 



The skiu of the perinceum continued from the scrotum, and partaking of 

 the characters it has on that part, is dark-coloured, thin, and extensible, 

 loosely connected with the subjacent textures, and in the male body studded 

 with crisp hairs. Around the anus, it is thrown into folds, which are 

 necessary to allow the extension of the orifice of the bowel, during the 

 passage of masses of frecal matter ; and along the middle of the perinseum 

 the median ridge or raphe of the scrotum is continued backwards to the 

 anus. By this mark upon the skin, the large triangle in which is comprised 



Fig. 713. 



Fig. 713. SUPERFICIAL DISSECTION OP THE PERINEUM AND PART OP THE THIGHS. 



a, superficial fascia ; &, accelerator urinse ; c, erector penis ; d, transversus perinaei ; e, 

 upper point of sphincter ani ; /, the edge of the gluteus maximus; 1, superficial perineal 

 artery ; 2, superficial perineal nerve. 



