COMMENTARY. Although we have treated succinctly of strangury and retention of urine in the Third Book, it may be proper, before explaining the ancient methods of introducing the catheter, to give some further account of the causes of these complaints, and the opinions entertained by the physiologists with regard to the functional offices of the urinary organs. Galen states that the bladder is possessed of two faculties, a retentive and an expulsive, both of which arise from muscular power; that the retentive resides in the neck of the bladder, and is of the voluntary kind of powers; but that the expulsive belongs to the class of natural or involuntary powers, being of the same kind as the peristaltic faculty of the intestines. When a person, then, makes water voluntarily, it is by suspending the voluntary action of the sphincter vesicæ, that is to say, of the retentive faculty of the bladder, whereby the expulsive or peristaltic powers are brought into action, and the contents of the bladder are thereby evacuated. He properly adds, however, that this involuntary or expulsive faculty may be assisted by the action of the voluntary muscles which surround the bladder, especially the recti muscles of the abdomen. Retention of urine, therefore, may arise from the loss of either of these faculties. The expulsive faculty is most commonly lost, either from over-distension of the bladder, as when its contents have been allowed to accumulate too far, or from injury of the spinal marrow which supplies it with nerves. Rhases remarks that when retention of urine proceeds from debility of the expulsive faculty, the bladder may be evacuated by merely making pressure above the pubes. According to Rhases, retention of urine arising from derangement of the retentive faculty, that is to say, from its no longer being under the control of the will, may be occasioned by inflammation, by some swelling, such as a fleshy tumour forming in the meatus urinarius, or by the presence of some foreign body, such as a stone, a clot of blood, or the like. He alludes several times to this fleshy tumour in the passage, by which he probably means either an enlargement of the prostate gland, or stricture of the urethra. He calls it a very intractable case. For a fuller exposition of the ingenious speculations and opinions stated above, see Galen (De Locis Affectis, iv, 4); Rhases (Contin. i and xxiii.)