BLADDER, the muscular organ that in man and the lower animals holds the urine. The kidneys secrete urine constantly, the blad der stores it and only empties itself at more or less definite intervals. In man the bladder is a flattened rounded to conical organ about the size of an orange, and holding under normal conditions about 16 ounces of urine (one pint). It is situated in the lower portion of the ab dominal cavity just behind the pubic bone, which serves as a protection. Its general shape is rounded triangular, the flat side being above, the ureters leading from the kidneys entering at the corners; the pointed end corresponding to the opening into the urethra, through which canal the urine is voided. The walls of the bladder are made up of several layers; the outer wall is of peritoneum in part, or serous and connective tissue combined. The greater part of the wall is made up of involuntary muscle fibres arranged longitudinally and cir cularly; the innermost 'coat is thin and delicate, — the mucous membrane,— and is lined through out by layers of regularly flattened squamous epithelial cells. The nervous supply of the bladder, by means of which it is emptied, is complex and probably threefold. It is under the influence of the vegetative nervous system of the hypagastric plexus; there are subsidiary centres in the spinal cord and higher up in the human cortex certain voluntary efforts have their influence on the bladder control. The primary receptor nerve cells of the vegetative system are in the bladder wall. These cause the bladder in the young infant, and also in the patient whose spinal cord control pathways are cut off, to be emptied and in the so-called irritable bladder it is probable that this part of the mechanism is mostly affected.
There is a very marked relation between the skin activities and the kidney and bladder ac tion, for while the skin is acting freely as in exercise in warm weather, a large amount of water is thus given off, which in cold weather is eliminated through the kidneys and thus by the bladder. This is noted daily when in cold
weather one leaves the warm house and shortly after walking in the cold of the outside air, the desire to urinate becomes urgent. Irrita bility of the bladder, particularly in children, and bedwetting is often a very troublesome complaint. It may be due to a variety of causes; excessive irritation, however, would probably not result in bedwetting, particularly in older children, if the control (inhibition) normally maintained by the brain were not cut off by deep slumber, thus permitting unconscious trends of the child to come to the fore. These unconscious trends are usually of an erotic na ture, hence the treatment by psychoanalysis is indicated. Infection of the bladder is very fre quent following gonorrhea and leads to many serious complications. (See CYSTITIS). Stones also develop in the bladder. See CALCULUS.
Paralysis of the bladder per se is a rare af fection; paralysis of the sphincter that controls the outlet may result from a variety of causes. It usually results in incontinence of urine. Re tention is an opposite condition and is fre quently due to loss of vegetative nerve action, such as follow labor, or an operation, or from the anmsthesia of opium, belladonna or similar narcotics. It may also be due to mechanical ob struction, in old men, particularly being due to an hypertrophied prostate gland. In many effeminate individuals weakness of the bladder is a symptom of conscious or unconscious masturbation. Weakness of the bladder with either retention or increased frequency of urination is a frequent early sign of severe nervous disorders, such as paresis, tabes, multiple sclerosis, tumor of the spinal cord. Consult Jelliffe and White, 'Diseases of the Nervous System' (1917).