THE INDIVIDUAL GROUPS OF PROTEINS 501 



and pipette. It should reach to a height of about one-quarter of the length 

 of the limbs and nearly to the top of the pipette. The gla s tube, B, above 

 the screw is sealed off. 



In order to determine the oxygen, it is necessary to know the volume of 

 the bottles, including the stoppers and about half of one limb of the gauge 

 to the nearest o-i c.c. and the pressure change indicated by the gauge in 

 terms of volume. 



The pressure change indicated by the gauge is determined by adjusting 

 the screw (with the taps open) so that a known volume, e.g. '2 c.c., is 

 driven from the pipette into the two limbs into which it passes equally. The 

 oil rises in these limbs and the rise is measured on the scale, 'i c.c. will 

 pass into each limb; it will produce a rise of r^ mm., i.e. a change of level 

 of r^ mm. of oil is given by 'i c.c. This should be determined for different 

 parts of the limbs. The volume of the bottles is ascertained by introducing 

 into the bottle a known volume of water, say 10 c.c., in order to reduce the 

 air space, lowering the level of the oil in the limbs with the taps open to the 

 air by altering the position of the screw, closing the tap on the side to be 

 measured and forcing a volume of air corresponding to *i c.c. into the bottle, 

 i e. by adjusting the screw so that the oil travels r^ mm. on the closed side. 

 The level of the oil on the other side is raised considerably ; the difference of 

 the levels (r 2 ) is noted. This is the pressure necessary to drive *i c.c into the 

 closed bottle. The volume is calculated from Boyle's law : 



In order to introduce into the bottle another volume V where V is the 

 volume of the bottle, atmospheric pressure would have to be exerted (io,ooc 

 mm. of clove oil) ; actually, a change of *i c.c. was produced by r a mm. : 



10,000 : V = r%\ 'i 



10,000 X 'I 



Hence V = - . 



*2 



To this must be added the 10 c.c. of water introduced. 



The oxygen content of blood is determined by putting into one of the 

 bottles 2 c.c. of dilute ammonia (4 c.c. of *88o sp. gr. to 1000 c.c. of water) 

 and running i c.c. of blood carefully beneath it. The stoppers are greased 

 and fitted and -3 c.c. of saturated ferricyanide solution is put into the little 

 tube. The boltles are put into a bath with gauge vertical until the temperature 

 is constant. This is shown by closing the taps to the air and observing if 

 there is a change of level in the manometer. The level is conveniently 

 adjusted about half-way up the limb. If there be a change, the taps are 

 opened again for a minute, closed and the gauge observed. As soon as the 

 temperature is constant, the tap to the air of the bottle not being used is 

 opened, the blood is laked by shaking with a rotatory motion for a minute, the 

 ferricyanide is emptied into the blood by turning the bottle and the oxygen is 

 liberated by shaking. The volume of the gas in the bottle and limb of the 

 apparatus is restored to its original level by adjusting the screw. The oil 

 rises in the other limb. The rise is measured = r z mm. Since the volumes 

 of the liquids (3*3 c.c.) introduced are known, the actual air space has a 

 volume V minus this amount = v r 



1 cmm. is the oxygen present in i c.c. of blood. 



10,000 



This volume must be corrected for temperature and pressure and tension of 

 aqueous vapour and for the actual volume of blood delivered by the pipette 

 (generally "96 instead of i c.c.). 



