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is hot, there is a relaxation of the vessels of the skin, with a more than ordinary flow of blood, which is thus withdrawn from the deeper organs.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. This vital fact is the key to the injurious results developed in the kidneys by the use of alcoholic drinks. These two organs have large blood-vessels conveying full amounts of blood to and from their structures, and they feel very quickly the presence of alcohol. Alcoholic liquors excite and irritate the delicate renal membranes, and speedily disturb and eventually destroy their capacity to excrete the proper materials from the blood.
The continued congestion of the minute structure of the kidney cuts off the needed nutrition of the organ, and forms the primary step in the series of disasters. Sometimes from this continued irritation, with the resulting inflammation, and sometimes from change of structure of the kidney by fatty degeneration, comes the failure to perform its proper function. Then, with this two-edged sword of disaster, the urea, which becomes a poisonous element, and should be removed, is retained in the system, while the albumen, which is essential to healthy blood, is filtered away through the diseased kidney.
259. Alcoholic Liquors as a Cause of Bright’s Disease. The unfortunate presence of albumen in the urine is often a symptom of that insidious and fatal malady known as albuminuria or Bright’s disease, often accompanied with dropsy and convulsions. One of the most constant causes of this disease is the use of intoxicants. It is not at all necessary to this fatal result that a person be a heavy drinker. Steady, moderate drinking will often accomplish the work. Kidney diseases produced by alcoholic drinks, are less responsive to medical treatment and more fatal than those arising from any other known cause.[[39]]
Experiment 129. Obtain a sheep’s kidney in good order. Observe that its shape is something like that of a bean, and note that the concave part (hilus), when in its normal position, is turned towards the backbone. Notice that all the vessels leave and enter the kidney at the hilus. Observe a small thick-walled vessel with open mouth from which may be pressed a few drops of blood. This is the renal artery. Pass a bristle down it. With the forceps, or even with a penknife, lift from the kidney the fine membrane enclosing it. This is the kidney capsule.
Divide the kidney in halves by a section from its outer to near its inner border. Do not cut directly through the hilus. Note on the cut surfaces, on the outer side, the darker cortical portion, and on the inner side, the smooth, pale, medullary portion. Note also the pyramids of Malpighi.