304 Appendix I. On methods 



See that the taps are open. 



Place the bottles on the stoppers with the pouches upwards. Place the apparatus 

 in the bath. 



After five minutes read, suppose the reading to be 



Left Right Error 



120 119-5 -5 



Close the taps and see that the surfaces do not move in one minute, then shake 

 for one minute at least or until the unsaturated blood ceases to change colour ; 

 replace in the water bath and shake alternately for a minute until a constant reading 

 is obtained. Suppose this to be 



Left Eight p 



110 129-5 19-5-0-5 = 19 mm. 



Measurement of C. 



Take the apparatus out of the bath, open the taps. Take off the left bottle, the 

 pouch of which should be clean and dry place a drop of ferricyanide in the pouch 

 and replace the bottle on the apparatus with the pouch downwards. Proceed to 

 measure the oxygen capacity. 



Let the measurement of C give a pressure of 60 mm. 



_ JQ\ 



The percentage saturation = 100 = 68 / . 



The corrections which must be applied to this will be found on p. 298. 



To expose blood to a gas of a given composition. 



Apparatus : 



A useful form of tonometer for the purpose consists of a cylindrical vessel of 

 250 c.c. capacity. 



FIG. 145. 



At one end the cylinder can be corked with a rubber stopper, at the other there 

 is a three-way tap. The bore of this tap is To mm. At the point A the tubing is 

 somewhat broader, so that there is a portion of the apparatus which will hold about 

 1 2 c.c. of blood when the apparatus is placed vertically. That portion of the 

 tubing between B and C requires to be made carefully if, as is sometimes the case, 

 the apparatus is expected to deliver a definite amount of blood into one of the bottles 

 of the small apparatus just described. 



