44 



PHYSICOCHKMICAL BASIS OF PHYSIOLOGICAL PROCESSES 



is done by placing the plasma in a separating funnel of 300 c.c. capacity, 

 laying the funnel on its side and displacing the air in it by alveolar air 

 secured by quickly making as deep an inspiration as possible through 

 the tube and bottle containing glass beads (Fig. 10). The glass beads 

 remove excess of water vapor from the air. The funnel must be restop- 

 pered before the end of the expiration, so that no outside air enters. It 

 is then rotated, for about two minutes, in such a way that the plasma 

 forms a film on its walls. If it is necessary to postpone the saturating 

 of the plasma, this should be pipetted off from the corpuscles and pre- 

 served in hard glass test tubes coated with paraffin. From ordinary glass 



Fig. 11. Van Slyke's apparatus for measuring the COa-cotnbining power of blood in blood plasma. 

 For description, see context. 



enough alkali is soon dissolved out to vitiate the results. After saturation 

 of the plasma with C0 2 , the funnel is placed in the upright position and 

 the plasma allowed to collect in the narrow portion, after which 1 c.c. 

 is removed with an accurate pipette and analyzed for C0 2 . 



The analysis may be done by using either the Van Slyke or the Hal- 

 dane-Barcroft apparatus. The Van Slyke method is as follows: 



The apparatus is filled to the top of the graduated tube with mercury 

 (Fig. 11) by raising the mercury reservoir F, care being taken that 

 D and E are also filled. One c.c. of the CO 2 -saturated plasma is then de- 



