656 THE URINARY ORGANS. 



Solid masses of fibrin and blood sometimes occur in the bladder, and may exist as 

 independent structures, or form nuclei for the deposit of urinary salts. 



For a detailed account of calculi, the conditions under which they form, modes of 

 analysis, etc., we refer to special works on this subject. 



The Urethra. 



Malformations . 



Some of the malformations of the urethra are described with those of the penis. 



The urethra may be impervious or may open at the root of the penis. More com- 

 monly there is partial obliteration or stricture of some part of the canal. The entire 

 urethra may be dilated into a sac. 



There may be a canal on the dorsum of the penis, formed by the fusion of the sper- 

 matic cords, and opening in the glans above the urethra. 



There may be two or more openings of the urethra. The canal may be dislocated 

 so as to open in the inguinal region. 



A number of cases have been reported in which a valve in the urethra has led to 

 hypertrophy of the bladder, dilatation of the ureters, and hydronephrosis. 



Owing to its narrowness, greater length, and peculiar connections with the internal 

 generative organs, the male urethra is much more liable to disease than the female. 



Changes in Size and Position. 



DILATATION of the urethra may be produced by strictures, or by calculi or other 

 bodies fixed in its lumen. The dilatations are fusiform or sacculated in shape, and may 

 reach the size of an orange or be even larger. 



STRICTURES of the urethra are usually due to inflammation of its walls. 



The stricture may be temporally, and due to a diffuse inflammatory swelling of the 

 mucous membrane, or by the raising of the relaxed membrane into a fold or pocket. 



Permanent strictures are produced by structural changes in the walls of the urethra. 



1. The mucous membrane and submucous tissue become thickened in inflammation 

 or as the result of injury and the new-formed fibrous tissue which contracts and narrows 

 the canal. 



2. Ulceration of the mucous membrane leaves cicatricial tissue, which contracts, 

 and also produces adhesions and bands of fibro'.is tissue (Fig. 418). 



FIG. 418. STRICTURE OF THE MALE URETHRA. 



3. There is fibrous induration of the corpus spongiosum and consequent constric- 

 tion of the urethra. 



