406 SURGICAL APPLIED ANATOMY. [Chap. XVIIT. 



that of the bulbous and membranous portions. It is 

 in the bulbous urethra that organic stricture is the 

 most commonly met with. The meatus measures 

 from one-fifth to one-fourth of an inch, and therefoi-e 

 if a catheter will pass the meatus it will pass along 

 any part of the canal if normal. Its aperture is very 

 resisting, and has often to be incised to allow the 

 larger instruments to pass. 



The narrowest parts of the urethra, therefore, are 

 at (1) the meatus, and (2) in the membranous segment, 

 especially at its anterior end. It is at these points that 

 calculi passed from the bladder are most apt to lodge. 

 The widest portions of the canal, on the other hand, are 

 at (1) the fossa navicularis, (2) the bulbous part of the 

 urethra, and (3) the centre of the prostatic portion. 



Keegan has shown that the urethra of a male 

 child two or three years of age will take a No. 9 

 catheter. In boys between eight and ten years a No. 

 1 1 lithotrite may be passed. 



It will be obvious, therefore, that the operation of 

 lithotrity may be performed upon quite young male 

 children, and that fragments of crushed calculus of no 

 small dimensions may be removed from the bladders 

 of such patients by washing. 



The mucous membrane presents, in addition 

 to many mucous glands, several lacunae, the orifices of 

 which for the most part open towards the meatus. 

 These lacunae are most numerous in the bulbous 

 urethra, and occxipy the floor leather than the roof of 

 the canal. In passing small catheters, therefore, the 

 jK)int of the instrument should be kept along the 

 upper surface of the tube, so that it may not become 

 engaged in any of these spaces. The largest Jacuna, 

 the lacuna magna, is situate in the roof of the fossa 

 navicularis, and may readily engage the point of a 

 small instrument. 



Otis has endeavoured to show that a definite 



