512 INFLUENCE OF X-RAYS ON PROPERTIES OF BLOOD 



general reaction of the animal, as regards the conditions of our investi- 

 gation. For the pH determinations we have employed the colori- 

 metric method developed by Cullen/ and for determining the bicar- 

 bonate content we have employed the procedure of Van Slyke.^ The 

 pH determinations have been checked electrometrically as have also 

 the standard buffer solutions used in the colorimetric tests. 



Preliminary observations showed the range of the pH value of 

 rabbit plasma to be between 7.12 and 7.26, values which are lower than 

 those stated by Hasselbalch and Lundsgaard (1912), 7.33 (electro- 

 metric), and Kurijama (1913), 7.4 to 7.5 (colorimetric). However, 

 since the electrometric method employed in obtaining our values is 

 more precise than was the method available at the time the values of 

 Hasselbach and Lundsgaard were determined, we believe our values 

 to be more nearly correct. We found the normal plasma bicarbonate 

 content, expressed in volumes per cent of CO2, to vary between 26 

 and 45. It is possible to obtain wide variations in a single rabbit un- 

 less careful attention is given to keeping the animal quiet during 

 the process of bleeding. Feeding also plays a role in the variations of 

 different samples of plasma but we have found it possible to control 

 this factor by standardizing the amount of food and the time of feed- 

 ing and the interval of time between the removal of animals from food 

 before the beginning of the experiment. 



The rabbits have been exposed to x-radiation from a Coolidge 

 tube, the dosage factors being as follows: spark gap, 3 inches; current, 

 10 milliamperes; target distance, 6 inches; and time of exposure, 15 

 minutes. This is a massive dose of radiation of relatively long wave 

 lengths, a large part of which are absorbed by the skin. This dose 

 approaches the maximum amount that can be given without killing 

 the animal and was purposely chosen as a starting point in order to 

 obtain clear cut results. The exposures were made directly on the 

 rabbit's abdomen which had been previously shaved. 



EXPERIMENTAL. 



1. Four rabbits were bled from the heart for plasma, then two of 

 the animals were exposed to the radiation stated. The other two 



^ CuUen, G. E., /. Biol. Chem., 1922, p. xvii. 



2 Van Slyke, D. D., J. Biol. Chem., 1917, xxx, 347. 



