196 DETERMINATION OF THE GASES OF THE BLOOD. [BOOK T. 



would attach to a knowledge of the actual weight of the blood 

 corpuscles. Determinations of the weight of the moist corpuscles 

 will probably in the future be rarely attempted. The following 

 very brief description of the one method which is to be recommended 

 above all others will suffice : it is based n^on finding the relative weight 

 of fibrin in the liquor sanguinis and in the blood (Hoppe-Seyler). 



This method, which can only be carried out when all suitable 

 preparations can be made before the blood is removed from the living 

 body, is as follows : 



Blood is received in a cylindrical (metallic) vessel which is sur- 

 rounded with Iceland at the same time another portion of 30 50 c.c. 

 of blood is collected and the fibrin determined in it by the proceeding 

 described at page 179. 



After an interval of an hour or two, the corpuscles having had 

 time to subside from the liquor sanguinis in the sample of blood 

 first collected, from 30 to 50 c.c. of the clear liquid are drawn off 

 by means of a cooled pipette and placed in a second apparatus for the 

 extraction of fibrin, and the process carried out exactly as in 

 the first case. The amount of fibrin being known, the operator is in 

 possession of the data required to be known. 



The calculation will be understood by quoting the following example 

 from v. Gorup-Besatiez. 



(1) the weight of fibrin in 1000 grammes of blood 



was found to be . . . . . 3 -95 grins. 



(2) the weight of fibrin in 1000 grammes of liquor 

 sanguinis was found to be . . . .8*07 grms. 



If 8 07 grms. of fibrin correspond to 1000 grms. of plasma, to how much 

 plasma will 3-95 grms. of fibrin correspond ? 



8-07 r'lOOO :: 3'95 : x 



Thus is found the weight of plasma in 1000 parts of blood, and the 

 weight of moist corpuscles is found, by subtraction, to amount to 

 1000-486-98 = 513-02. 



Separation and Determination of the Gases of the Blood. 



The methods now universally adopted and alone to be recom- 

 mended for the extraction of the gases of the blood consist in 

 introducing an accurately determined volume of blood into the 

 vacuum of a mercurial air-pump, exposing it to a temperature of 

 40 45 C., removing the gases pari passu with their disengagement, 

 collecting them over mercury, and then subjecting them to analysis. 

 Whilst the principles which guide these operations are very similar, 



1 A vessel constructed on Dr Sanderson's plan (Fig. 9, p. 32) should be used for 

 this experiment. 



