Unusual constituents of the urine are albumen, sugar, and bile.  When albumen is present in urine, it often indicates some disease of the kidneys, to which the term albuminuria or Bright’s Disease is applied.  The presence of grape sugar or glucose indicates the disease known as diabetes.  Bile is another unusual constituent of the urine, appearing in jaundice.

The bladder is situated in the pelvic cavity or in the lowest part of the abdomen.  When full, the bladder is pear-shaped; when empty, it is collapsed and lies low in the pelvis.  The functions of the bladder are to collect and retain the urine, which has reached it drop by drop from the kidneys through the ureters, until a certain quantity accumulates, and then to expel it from the body.

[Illustration:  Fig. 109.—­Vertical Section of the Back. (Showing kidneys in situ and the relative position of adjacent organs and vessels.) [Posterior view.]

  A, 12th dorsal vertebra;
  B, diaphragm;
  C, receptaculum chyli;
  D, small intestines
]

In the kidneys, as elsewhere, the vaso-motor nerves are distributed to the walls of the blood-vessels, and modify the quantity and the pressure of blood in these organs.  Thus, some strong emotion, like fear or undue anxiety, increases the blood-pressure, drives more blood to the kidneys, and causes a larger flow of watery secretion.  When the atmosphere is hot, there is a relaxation of the vessels of the skin, with a more than ordinary flow of blood, which is thus withdrawn from the deeper organs.  The blood-pressure in the kidneys is not only diminished, but the total quantity passing through them in a given time is much lessened.  As a result, the secretion of the kidneys is scanty, but it contains an unusual percentage of solids.

When the atmosphere is cold, the reverse is true.  The cutaneous vessels contract, the blood is driven to the deeper organs with increased pressure, and there is a less amount of sweat, but an increased renal secretion, containing a smaller proportion of solids.  Certain drugs have the power of increasing or diminishing the renal secretion.  As the waste matters eliminated by the kidneys are being constantly produced in the tissues, the action of the renal organs is continuous, in marked contrast with the intermittent flow of most of the secretions proper, as distinguished from the excretions.

258.  Effects of Alcoholic Drinks upon the Kidneys.  The kidneys differ from some of the other organs in this:  those can rest a while without any harm to themselves, or to the body.  We can keep the eyes closed for a few days, if necessary, without injury, and in fact often with benefit; or, we can abstain from food for some days, if need be, and let the stomach rest.  But the kidneys cannot, with safety, cease their work.  Their duty in ridding the blood of waste products, and of any foreign or poisonous material introduced, must be done not only faithfully, but continually, or the whole body at once suffers from the evil effects of the retained waste matters.