Volume 1

A text-book of physiology / by Henry P. Bowditch [and others] ; edited by William H. Howell.

Date:
1900
Catalogue details

Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: A text-book of physiology / by Henry P. Bowditch [and others] ; edited by William H. Howell. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    of the acid.^ In a similar manner acids formed from decomposing proteid may be neutralized (see ])p. 506 and 550). The ammoniacal fermentation of the urine consists in the decomposition of urea into ammonium carbonate by the micrococcus urince, the urine becoming alicaline. Compounds of Nitrogen with Oxygen.—There are various oxides of nitrogen, the higher ones being powerfully corrosive, and some of these unite with water to form acids, of which nitric acid (HNO3) is the strongest. Only nitrous and nitric oxides are of physi- ological interest. Nitrous Oxide, likewise called laughing-gas, is prepared by heating ammo- nium nitrate, NH,N03 = N,0 + 2HA It supports ordinary combustion almost as well as pure oxygen, but it will not sustain life. Mixed with oxygen it may be respired, producing a state of unconsciousness preceded by hysterical laughter. Nitric Oxide, NO, is prepared by dissolving copper in nitric acid, 3Cu + 8HNO3 = 3Cu(N03)2 + 4H,0 + 2N0. Contact with oxygen converts it into peroxide of nitrogen (NO.2), which is an irritating in-espirable gas of reddish color. Nitric oxide in blood first unites with the oxygen of oxyhsemoglobin, forming the peroxide (NO2), and then the nitric oxide combines with haemoglobin, forming a highly stable compound, nitric-oxide hasmoglobin (Hb-NO). Nitrogen in the Body.—Nitrogen is taken into the body combined in the great group of proteid substances, which are normally completely absorbed by the intestinal tract. It passes from the body in the form of simple decom- position-products, in larger part through the urine, but likewise through the juices which pour into the intestinal canal. The unabsorbed residues of these latter juices, mixed with intestinal epithelia constitute in greater part the feces.^ An almost insignificant amount of nitrogen is further lost to the body through the hair, nails, and epidermis, but, generally speaking, the sum of the nitrogen in the urine and feces corresponds to the proteid decomposition for the same time (1 gram N = 6.25 grams proteid). When the nitrogen of the proteid eaten is equal in quantity to the sum of that in the urine and feces, the body is said to be in nitrogenous equilibrium. When the ingested nitrogen has been larger than that given oflF, proteid has been added to the substance of the body; when smaller, proteid has been lost. These propositions were established by Carl Voit. A small amount of urea and other nitrogenous substances may be excreted in profuse sweating. Proteid nitrogen never leaves the body in the form of free nitrogen or of ammonia. That ammonia is not given off by the lungs may be demonstrated by perform- ing tracheotomy on a rabbit, and passing the expired air first through pure potassium hydrate (to absorb CO..) and then through Nessler's reagent. The experiment may be continued for hours with negative result.' ' Fr. Walther: Archiv fiir exper. Pathologie und Pharmakologie, 1877, Bd. 7, S. 164. ^ Menichanti and Prausnitz: Zeitschrifl fur Biologie, 1894, Bd. 30, S. 353. 2 Bachl,: Zeitschrifl fiir Biologie, 1869, Bd. 5, S. 61.