Animal physiology / by John G. M'Kendrick.

  • John Gray McKendrick
Date:
1877
Catalogue details

Licence: Public Domain Mark

Credit: Animal physiology / by John G. M'Kendrick. Source: Wellcome Collection.

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    formed before urea. In rapid-breathing, warm-blooded animals, uric acid is rapidly oxidised to urea, and con- sequently only a small amount of the acid appears in the urine; whereas, in slow-breathing, cold-blooded animals, the oxidation is incomplete. Man being omnivorous, partakes of enough of food rich in carbon to prevent the complete oxidation, and therefore a small amount of uric acid is always found in his urine. The kidneys also separate inorganic matters, such as chlorides, sulphates, phosphates, &c. These, as well as the urea, are much modified as to amount by the nature of the diet, and the amount of fluid taken with them. 154. Special Characters of the Urinary Seci'etion.—Urine is a clear, amber-coloured, faintly acid fluid, with a bitterish taste, and an aromatic odour. It contains (i) water; (2) a small amount of mucus from passages; (3) urea, from the oxidation of nitrogenous matter ; (4) uric acid, in the form of urates of soda and potash ; (5) a num- ber of less oxidised bodies in small quantities, such as allantoin, xanthin, creatin, creatinin, &c.; (6) colouring matter ; (7) odor- iferous matter ; (8) salts, chiefly chlorides of sodium and potassium, sulphates of soda and potash, phosphates of soda and potash, phos- phate of lime, and phosphate of magnesia ; (9) a trace of sugar ; and (10) small quantities of the gases oxygen, carbonic acid, and nitrogen. In flesh-eating animals, urea is present in large amount; very little uric acid being found; but in the urine of vegetable feeders, little urea and no uric acid are present, while hippuric acid exists in large amount. 155. Conditio7i5 influencing the amount of Urine.—The normal amount is from 50 to 60 ounces daily. It is less in summer than in winter. The amount seems to depend (i) on the intensity of the pressure of the blood within the Malpighian tufts ; and (2) on the quantity of water or other diffusible matter taken into the system. 156. Separation and Discharge of the U^'ine.—The urine is con- stantly being secreted by the kidney. It is carried away to the bladder by a tube called the ureter—the bladder serving as a reser- voir. It collects in the bladder until that organ is completely filled, when it is voided by contraction of the walls of the bladder, aided by the abdominal muscles. The evacuation is partly volun- tary and partly involuntary.
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