78 THE GASES OF THE BLOOD. 



closed upper portion two platinum wires, p n, are soldered. The eudiometer is 

 closed below by mercury. 



Estimation of the Carbon Dioxid. A globule of potassic hydrate fused to a 

 platinum wire and moistened on its surface is brought from below through the 

 mercury into the gaseous mixture. The carbon dioxid unites with the potassium 

 hydrate to form potassium carbonate. After remaining in place for a considerable 

 period of time, the globule is removed in the same way. The diminution in the 

 volume of the gases indicates the volume of the carbon dioxid removed. 



Estimation of the Oxygen. In the same way as in estimating the carbon dioxid 

 a globule of phosphorus is introduced into the eudiometer-tube by means of 

 a platinum wire and which takes up the oxygen for the formation of phosphoric 

 acid; or a dry globule of coke or papier mache saturated with a solution of pyro- 

 gallic acid in potassic hydrate, which eagerly takes up oxygen. After removal of 

 the globule the diminution in volume of the gases indicates the amount of oxygen. 



The oxygen can be determined most accurately and most rapidly, according 

 to Volta and Bunsen, by explosion in the eudiometer. An abundance of hydro- 

 gen, whose volume is carefully determined, is introduced into the eudiometer- tube. 

 Then an electric spark is made to pass through the tube between the wires p and 

 n. The oxygen and the hydrogen combine to form water. In consequence a 

 reduction in the volume takes place in the eudiometer, of which a third represents 

 the oxygen required for the formation of the water. 



Estimation of the Nitrogen. If the carbon dioxid and the oxygen are removed 

 from the gas-container according to the methods described the remainder consists 

 of nitrogen. 



SPECIAL FACTS CONCERNING THE GASES OF THE BLOOD. 



Oxygen is present in arterial blood from the dog on an average to the 

 amount of 18.3 volumes per cent., at a temperature of o C. and i meter of 

 mercurial pressure. Arterial blood is saturated, according to Pfltiger, 

 to T 9 Q-, according to Hiifner that of the dog to |i> with oxygen. 

 By means of thorough artificial respiration in animals in the state 

 of apnea or by active agitation of the blood with air the amount of 

 oxygen can be brought up to 23 volumes per cent. Venous blood con- 

 tains on the average 8.15 volumes per cent, less of oxygen than arterial 

 blood, although the amount of oxygen varies widely in accordance 

 with the tissues and the circulatory conditions. Sczelkow found 

 6 volumes per cent, in the blood of resting muscles. Only traces are 

 present in the blood after asphyxiation. In the more highly colored 

 blood of active glands, such as the salivary glands and the kidneys, 

 oxygen is undoubtedly present in larger amount than in ordinary, 

 darker venous blood. 



The oxygen occurs in the blood as follows: 



(a) From o.i to 0.2 volume per cent, are in a state of simple absorp- 

 tion in the plasma thus only a minimal portion, not exceeding that 

 which distilled water at the temperature of the blood and at the partial 

 pressure of oxygen in the air of the lungs would take up. 



(b) Almost all of the oxygen of the blood is combined chemically, 

 and with the hemoglobin of the erythrocytes, with which it forms oxy- 

 hemoglobin ; it is therefore not subject to the laws of absorption. 

 The total amount of blood acts with regard to the chemical absorption 

 of oxygen like a gas-free solution of hemoglobin, except that the absorp- 

 tion of oxygen by the blood takes place more rapidly than by a solution 

 of hemoglobin. At a temperature of o and at moderate atmospheric 

 pressure 760 mm. of mercury i gram of hemoglobin takes up from 

 1.6 to 1.8 cu. cm. of oxygen according to Hiifner 1.592 cu. cm. 



