902 



PHYSIOLOGY 



the oxygen-binding power of this fluid is entirely dependent on the 

 amount of haemoglobin it contains. For this purpose we may make use 

 of the fact discovered by Haldane, that the combined oxygen in oxy- 

 hsemoglobin is liberated rapidly and completely on addition of a solution 

 of potassium ferricyanide to laked blood, and may thus be easily measured 

 with the help of an apparatus similar to that used for determining urea in 

 urine by the hypobromite method. 



The following description of the method is given by Haldane : 



' Twenty cubic centimetres of the oxalated or defibrinated blood, thoroughly 

 saturated with air by swinging it round in a large flask, are measured out from a pipette 

 into the bottle A, which has a capacity of about 120 c.c. As it is important to avoid 



FIG. 381. Haldane's method for determining the oxygen capacity of the blood. 



blowing expired air into the bottle, the last drops of blood are expelled from the pipette 

 by closing the top and warming the bulb with the hand.' Thirty cubic centimetres 

 are then added of a solution prepared by diluting ordinary strong ammonia solution 

 (sp. gr. 0-88) with distilled water to 71 -J^. The ammonia prevents carbonic acid from 

 coming off, while the distilled water lakes the corpuscles. The blood and ammonia 

 solution are thoroughly mixed by shaking, and at the end of this operation the solution 

 should appear perfectly transparent when tilted up against the sides of the bottle. 1 

 About 4 c.c. of a saturated solution of potassium ferricyanide are then poured into the 

 small tube B (the length of which should .slightly exceed the width of the bottle) and 

 placed upright in A. The rubber stopper, which is provided, as shown, with a bent 

 glass tube connected with the burette by stout rubber tubing of about 1 mm. bore, is 



1 If the solution were not transparent this would indicate that the laking was 

 incomplete, and more ammonia solution would need to be added. 



