ADVANCED DEMONSTEATIONS 407 



containing a known percentage of carbonic oxide (about '06 per 

 cent.) is aspirated at a rate of about '5 to 1 litre per minute. 

 The animal is allowed to breathe the mixture of gases till the haemo- 

 globin of its blood is saturated with CO to the maximum for the 

 percentage of gas present. The bottle is then disconnected and rapidly 

 plunged under water, so that the animal is drowned. 



Normal blood when sufficiently diluted gives a yellow, and carbonic 

 oxide blood a pink colour. If blood be diluted 100 times, and a portion 

 of it be saturated with CO, it requires somewhat more than an equal 

 volume of standard carmine solution l to bring the unsaturated portion to 

 the same tint and intensity of colour as the saturated portion. The exact 

 relation of the carmine solution to the blood solution is determined by trial. 



Narrow test tubes, A, B, C, similar to Gower's haemoglobinometer 

 tubes are employed. 2 c.c. of water is measured from a narrow burette 

 into A. '02 c.c. of blood is obtained by opening the heart of the mouse 

 immediately after its death. The blood is measured in the pipette of 

 Gower's haemoglobinometer and mixed with water in A. A similarly 

 diluted solution of normal mouse's blood is well shaken with coal gas 

 in a test tube. This is then placed in B, which is filled full and corked. 



It is then determined how much carmine must be added to a third 

 sample C of normal diluted blood (1) to make it equal in tint to A, 

 (2) to B. The carmine is added from a narrow burette *1 c.c. at a 

 time. Suppose '5 c.c. carmine must be added to C to make its tint- 

 equal A, and 2*2 c.c. to produce equality of tint with B, then A 



5 4*2 



is ^ x x 100 = 38% saturated. 



Z'D A'A 



The calculation of the oxygen tension is made by finding the 

 percentage of CO in air to which the actually observed saturation 

 of the blood corresponds, 2 dividing 20'9 by this, and multiplying by 

 the actual percentage of CO in the air breathed. 



1 Stock Solution. One grm. of pure carmine is mixed in a mortar with a few 

 drops of ammonia, and dissolved in 100 c.c. of glycerin. Standard Solution. 

 5 c.c. of the stock solution is added to 500 c.c. of water. This must be prepared 

 fresh. The amount required to render normal diluted blood equal to the sample 

 of diluted blood saturated with CO must be found at each determination, for the 

 carmine tint varies slightly with daylight. 



2 See the curve of dissociation of COHb in air which has been constructed by 

 Haldane and L. Smith, Journal of Physiology, xxii., p. 233. The following are 

 some of the data from which the curve was constructed : 



Ox-blood 1 % solution % CO. Temp. % Saturation of Hb with CO. 



was shaken with '195 37 C. 74 "6 



air containing -125 64 '3 



086 54-8 



069 48-5 



037 36-4 



