Chap. xvin.] THE URETHRA. 407 



relation exists between the circumference of the penis 

 and the circumference of the urethra, a relation 

 represented by the proportions 2 '25 : 1, and makes 

 use of instruments of large size, which, when passed, 

 seem to demonstrate rather the dilatability of the canal 

 than any certain anatomical relationship. 



The urethra may be ruptured by the patient 

 falling asti'ide of some hard substance. In such an 

 injury it is crushed between the hard substance 

 and the pubic arch. The part of the canal, there- 

 fore, that is most often damaged is the membranous 

 segment, and the posterior part of the penile 

 division. The more the body is bent forwards at the 

 time the perineum is struck, the greater is the length 

 of penile urethra that may be crushed against the 

 pubes. 



The female urethra is about one and a half 

 inches in length, and has a diameter of from a quarter 

 to one-third of an inch. It is capable, however, of 

 great distension. In the erect position the canal is 

 nearly vertical, and in the recumbent posture almost 

 horizontal. 



Penis. The skin covering the bulk of the organ 

 is thin and fine, and the subcutaneous tissue is scanty 

 and lax. It follows, from the looseness of this tissue, 

 that the skin is very distensible and movable. The 

 latter fact should be borne in mind in circumcision, 

 for in performing that operation the skin of the penis 

 can be so readily drawn forwards over and beyond the 

 glans, that if it is excised as far back as possible the 

 greater part of the organ may be left bare. This 

 applies, of course, mainly, to children. The laxity of 

 the subcutaneous tissue permits the organ to become 

 enormously swollen when oedematous, or when extra- 

 vasated urine finds its way into the part. Over the 

 g'ans penis the mucous membrane is so adherent 

 that there is practically no subcutaneous tissue. }t 



