Physiology and biochemistry in modern medicine . ome quickly destroyed is added to theblood. By determining the concentration of this substance in a speci-men of blood, the volume with which it has become mixed can readily becalculated. Acacia has recently been found suitable for this purpose(Meek), but the best known work (of Haldane) was done by causing theanimal to inspire a known amount of carbon monoxide. This combineswith the hemoglobin of the blood (see page 401) to displace an equalquantity of oxygen. By determining the difference between the volume BLOOD IKKSKIKK 137 of carbon monoxid
Physiology and biochemistry in modern medicine . ome quickly destroyed is added to theblood. By determining the concentration of this substance in a speci-men of blood, the volume with which it has become mixed can readily becalculated. Acacia has recently been found suitable for this purpose(Meek), but the best known work (of Haldane) was done by causing theanimal to inspire a known amount of carbon monoxide. This combineswith the hemoglobin of the blood (see page 401) to displace an equalquantity of oxygen. By determining the difference between the volume BLOOD IKKSKIKK 137 of carbon monoxide in the Mood before and following its administrationwe can calculate with how much blood the known inspired quantity ofcarbon monoxide must have combined. The results vary somewhat indifferent animals; in the dog, the blood constitutes about per centof the body weight, and in man, about 5 per cent. The immediate effect of hemorrhage on the blood pressure depends onthe rate of bleeding. If a large artery, such as the femoral, is cut across,. Ti**« •rAfrsti^A Fig. 29.—Effect of stimulation of the left splanchnic nerve on the arterial blood the primary and secondary rises. the pressure will show an immediate but moderate fall, due largely to thefact that we have suddenly decreased the peripheral resistance. If onthe other hand only a small artery or a vein is opened, the bleeding willat first produce no effect on the blood pressure, and it is only after someconsiderable amount of blood has been removed that it begins to fall (). To be more exact, we may state that the removal of 5 of blood perkilogram of body weight does not influence the blood pressure. The re-moval of a second portion of 5 per kilogram causes the blood pres-sure to begin to fall, the fall of pressure for each subsequent 5 of 138 THE CIRCULATION OF THE BLOOD blood per kilogram removed averaging about 6 mm. Hg, until after 20to 25 of blood per kilogram have been re
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