500 RESPIRATION 



mits the air from the receptacle G and the rest of this connecting tube to enter the 

 chamber B. This process is repeated until a high vacuum has finally been attained. 

 A measured quantity of blood is then allowed to flow from the graduated cylinder 

 K into the receptacle G which is surrounded by warm water to hasten the escape 

 of the gases. The blood boils in this vacuum, but is prevented from boiling away 

 by the condenser. The gases given off by it are then collected over the mercury. 



It is also possible to determine the quantity of oxygen or carbon dioxid in a 

 chemical way without the use of the pump. Thus, the CO2 may be liberated by 

 adding diluted acids to the blood and by collecting it in potassium hydrate. ^ 

 Schultze^ has described a simple volumetric method for the estimation of CO2 

 which Rielander has applied to the analysis of the CO2 in the blood. In recent 

 years Haldane^ has devised an apparatus which has been modified by Fr. Miiller.* 

 It is based upon the principle that the oxygen in hemoglobin may be ascertained in 

 a quantitative manner by adding a solution of potassium ferricyanid to laked blood. 

 The apparatus consists of a bottle which is connected with a receptacle containing 

 the solution just mentioned. It also communicates with two burets united below 

 by a connecting piece. The second buret is joined to a bottle which is used as a 

 thermobarometer. A tube leads from the T-cannula to a niveau receptacle filled 

 with slightly acidified water. To the central bottle are attached two glass bulbs 

 separated from one another, as well as from the bottle, by stop-cocks. The upper 

 bulb contains a dilute solution of ammonia and the lower, th^ blood to be ex- 

 amined. 



A perfect constancy of the temperature having been attained, note is made of 

 the level of the water in the burets. If the blood and the solution of ammonia are 

 now permitted to flow into the central bottle, the former will be laked immediately. 

 Under repeated shaking the ferricyanid is then added to the blood after which the 

 level of the water in the burets is observed at intervals. Its maximal fall in the 

 buret nearest the generator indicates the volume of oxygen evolved. In these 

 determinations close attention must also be paid to the temperature as well as to 

 the barometric pressure. 



Haldane and Barcroft^ have given to this apparatus a more convenient form 

 so that even very small quantities of blood may be examined (Fig. 257). Moreover, 

 Mosso and Marro^ have proved that this procedure may be made to include a 

 determination of the carbon dioxid content of the blood. Tartaric acid is em- 

 ployed for the liberation of this gas. The same apparatus may also be employed 

 as a differential indicator of these gases in two different samples of blood. ^ 



In the latter case the apparatus consists of two bottles of equal size (Fig. 257) 

 which are connected with a manometer (1.0 mm. bore) filled with oil of cloves of 

 known specific gravity. Into one of these receptacles are then poured 1 c.c. of blood 

 and 2 c.c. of ammonia, made by adding 4 c.c. of strong NH3 to a liter of water. The 

 blood having been thoroughly laked, the stoppers are anointed with vaselin and 

 their inside compartments filled with 0.2 c.c. of a saturated solution of potassium 

 ferricyanid. The apparatus is then placed in a water bath for about five minutes 

 with both stop-cocks open. At the end of this period the ferricyanid solution is 

 allowed to trickle into the laked blood under repeated shaking of the entire appara- 

 tus. It is then replaced in the water bath. The column of the oil of cloves at the 

 side of the blood is now brought to its original level by means of the screw clamp, 

 after which the difference in the levels on the two sides is noted. The volume of the 



oxygen evolved equals x = ?/ ( — j in which y stands for the difference of level 



1 F. Kraus, Archiv fur exp. Path., xxvi, 1890. 



2 Zeitschr. ftir die landw. Vers, in Oesterreich, 1905. 

 8 Jour, of Physiol., xxii, 1898 and xxv, 1900. 



* Pfiiiger's Archiv, ciii, 1904, 541. 



6 Jour, of Physiol., xxviii, 1902, 232. 



* Rend, della R. Acad, dei Lincei, xii, 1903. 



^ Barcroft, Jour, of Physiol., xxxvii, 1908, 12. 



