NEUTRON EFFECTS ON ANIMALS 137 



animals irradiated for other studies. Cages 4 and 5 (9) were used as the 

 containers for the rabbits during irradiation. 



Ahsorption Spectra. Absorption spectra were obtained using Hilger 

 echelon cells (10) with a medium-sized Bausch and Lomb quartz spectro- 

 graph by technique previously described (11). The light used was from 

 a water-cooled, low-voltage hydrogen arc (12), giving a continuous spec- 



o o 



trum from about 1850 A to 5000 A. Photographs were taken with East- 

 man 33 plates. 



The actual distances on the photographic plates were: ultraviolet, 1900 A 

 to 4000 A, 15.6 cm.; 3000-5000 A, the range covered bv the hemoglobin 

 absorption, 7.25 cm.; and 3700-4700 A, the spread of the main peak of 

 hemoglobin, 2.5 cm. Consequently, the position of the hemoglobin ab- 

 sorption maximum could not be determined with, the same accuracy as 

 could the plasma protein maximum, but the convenience of using the same 

 apparatus for both purposes outweighed this consideration for this ex- 

 ploratory work. 



Plasma and Hemoglobin Solutions. The blood (about 5 ml.) was obtained 

 bj^ heart puncture and placed in a tube containing drj^ lithium oxalate pow- 

 der as an anticoagulant. Food, except water, was witliheld from the 

 animals overnight before bleeding so that none of the plasma showed any 

 turbidit3^ After centrifuging the blood, the bulk of the plasma was 

 pipetted into sterile serum vials, after which the remainder of the plasma, 

 the white cells and some of the red blood cells, were pipetted off and dis- 

 carded. The remaining red blood cells were stirred up and used in the 

 preparation of the corresponding hemoglobin solution. 



The plasmas were diluted to one-sixth their original concentrations ^nth 

 distilled water and used without further preparation. The hemoglobin 

 solutions were prepared by adding 0.5 ml. of red blood cells to distilled 

 water to make 100 ml. of solution in a volumetric flask, thoroughly mixing 

 and allowing the solutions to stand at room temperature for 1 hour, fol- 

 lowed by the centrifuging of about 5 ml. of the solution to remove cell de- 

 bris. The above concentrations were chosen so that complete, unbroken 

 absorption curves could always be obtained. 



Except during the time required for the preparation of the solutions, 

 the blood and the solutions were kept at refrigerator temperature until 

 used. The absorption spectra were generally obtained within 48 hours after 

 the blood was drawn. 



DISCUSSION 



The results obtained, together with the pertinent experimental data, 

 are given in Table I. Two absorption curves are shown in Fig. 1 : "A" for 

 the plasma solution, "B" for the hemoglobin solution obtained from the 



