Y. Henderson and A. H. Smith 43 
water, and injecting the blood with the hypodermic syringe. 
But this refinement takes time and requires extreme care to 
avoid admitting the least trace of air. 
CO, Determination. 
The CO, content of the blood is determined in exactly the 
same manner and with the same tube, merely using the tartaric 
Fig. 3. A, gas burette of analyzer; B, diffusion tube; C, beaker of water. 
acid solution instead of ferricyanide. (When the amount of gas: 
in the blood is very high it is advisable to use only half quanti- 
ties of blood and reagent; namely, 0.75 ec. of ammonia, 0.5 cc. of 
blood, and 0.10 cc. of tartaric acid.) Owing to the solubility of 
CO, it is necesary in the calculation of the results to take into 
account that part of the gas which remains in solution in the 
