130 EXPERIMENTAL PHYSIOLOGY. 



cyanide in the small flat-bottomed tube (A). About 15 c.c. of 

 defibrinated blood is exposed in a 250 c.c. flask, to alveolar air 

 obtained by expiring deeply into the flask and rotating so that the 

 blood forms a film on the walls. The blood will become saturated 

 with oxygen and it will take up CC>2 until there is equilibrium be- 

 tween the tensions of this gas in the air and blood. (Is this all the 

 CC>2 with which the blood could combine?) The rotation should be 

 kept up for about two minutes, the air in the flask being meanwhile 

 repeatedly replaced by alveolar air. 



Immediately it has settled to the bottom of the flask, 10 c.c. 

 of the blood is removed by the pipette and, after wiping the tip 

 with a cloth, slowly delivered under the ammonia solution in the 

 bottle. The bottle is then gently shaken until the blood is com- 

 pletely laked and a transparent red solution is obtained. (In cases 

 where the blood is not saturated with oxygen, as, for example, in 

 venous blood, it is necessary to postpone the laking process until 

 after the bottle has been closed and connected with the burette, 

 since otherwise C>2 would be absorbed from the air) . Having placed 

 the flat-bottomed tube (A) upright in the bottle and with the air 

 outlet of the burette (B) open, the stopper is firmly inserted into 

 the bottle, which is then immersed in the water bath, and the water 

 stirred. Whenever the fluid in the burette ceases to move further 

 indicating that the temperature of the air in the bottle has become 

 the same as that of the water bath the stopcock B is again opened 

 to allow the meniscus of fluid in the burette to return to the zero 

 mark. 



To displace the oxygen, the bottle is removed from the water 

 bath, and while holding it in a towel, to prevent its becoming 

 warmed by the hand, it is tilted so that the ferri cyanide spills into 

 the laked blood. The bottle is shaken for about one minute without 

 allowing the contents to come in contact with the stopper or tubing. 

 The expelled oxygen depresses the fluid in the burette, and as it does 

 so, the levelling tube should be lowered so that there may not be 

 increased pressure in the apparatus, which would encourage leaks. 

 The bottle is returned to the water bath, and the water stirred 

 until the level of fluid in the burette remains constant. The reading 

 on the burette, taken when the levels of fluid in it and the levelling 

 tube are exactly the same, gives the c.c. of oxygen expelled from 



