A very important lesion of this structure is Hypertrophy. The common enlargement of old age is due chiefly to increase of the muscular substance. This enlargement exists in about 30 per cent, of men above 60 years of age. It develops slowly without any apparent cause, and in this respect has the characters of a tumour. Sometimes the prostate enlarges uniformly, and it may reach the size of the fist. But sometimes, with or without a general enlargement, there is a more local hypertrophy, forming the so-called third lobe of the prostate, which projects inwards at the neck of the bladder, and is sometimes so large as to act like a valve to the orifice of the urethra. This third lobe scarcely exists as a visible lobe when the normal prostate is examined after laying open the bladder, and when thus visible it is entirely a new-formation. The effect of enlargement of the prostate on the urethra is to be noted. If there is a general enlargement the urethra is necessarily elongated in its prostatic portion, and whereas normally this portion measures 1 1/2 inches in length it may come to be 4 inches. At the same time the tube may be narrowed and even distorted. If, for instance, the central part of the prostate part is specially hypertro-phied, then 'the urethra, being pushed upwards, has on section a crescentic shape with the convexity upwards; or if one side is larger than the other, there will be a convexity towards the opposite side.

Besides this muscular hypertrophy the more unusual hypertrophy of the glandular structure is to be mentioned. The glandular structure may increase with the muscular, but sometimes enlarges by itself, so that we have an adenoma of the prostate.

Cancer of the prostate is not of frequent occurrence. The gland enlarges and the disease is apt to extend to neighbouring structures.

Tuberculosis occurs not infrequently in the prostate and vesiculae seminales in conjunction with similar disease in other parts of the genitourinary passages. There is caseous necrosis with ulceration as usual, and this may cause even perforation into the rectum or bladder.

Concretions are of very frequent occurrence in the prostate in old persons. They are formed in the gland-ducts and are of various sizes, from very minute to the size of a grain of corn. When small they are colourless, but as they enlarge they frequently become blackish or reddish brown in colour. They are round or oval in form and frequently present concentric stratification. They have usually a central cavity. These bodies mostly present the character of amyloid bodies, giving a bluish or mahogany red colour with iodine, and the usual bright red colour with methylviolet (see under Amyloid Degeneration). Often they contain lime salts in their substance. They may pass into the urethra and escape with the urine. While in the prostate they do not as a rule produce much disturbance.