REFRACTOMETRIC METHOD 65 



Refractive index of the serum 1 . 34686 



Refractive index of distilled water 1 . 32887 



Difference 0.01799 



Refractivity of the proteins = 0.01799 - 0.00244 = 0.01555 

 Refractivity of the globulins = 0.01555 - 0.00759 = 0.00796 

 Concentration of globulins = Iff = 3.5 per cent 

 Concentration of total proteins = 3.5 + 4.3 = 7.8 per cent 



Since the percentage of total proteins is dependent upon the 

 dilution of the blood and is therefore highly variable, while the 

 relative proportions of globulin and albumin are much more 

 constant, it is convenient to express these in percentages of the 

 total proteins. Thus in the above result, taking the total pro- 

 teins as 100, we find that the globulins formed 45 per cent and 

 the albumins 55 per cent of the total proteins. 



This method has been applied to the study of the proteins in 

 human blood-serum under normal conditions and a variety of 

 disease-conditions by A. H. Rowe (25) (26) (27) (31). It has 

 also been applied to the study of the changes in the ratio of 

 globulin to albumin in blood-serum during immunization and 

 infection by Righetti (17), Hurwitz and Meyer (4) and Schmidt 

 (28). The globulins, albumins and non-proteins in the blood- 

 sera of a variety of mammals and birds have also been estimated 

 refractometrically and characteristic differences found in the 

 relative proportions of these constituents in widely-separated 

 classes of animals (2) (3) (5) (23) (30) (33) (34). 



The refractometric method has also been applied to the esti- 

 mation of casein in milk (20) and to the estimation of the diges- 

 tive activity of proteolytic ferments (22) (29). 



LITERATURE CITED 



(1) Arny, H. V., and Pratt, T. M., Amer. Journ. of Pharmacy 78 (1906), 



p. 121. 



(2) Briggs, R. S., Journ. Biol. Chem. 20 (1914), p. 7. 



(3) Buck, L. W., Journ. of Pharmacology and Exper. Therap. 5 (1913), 



p. 553. 



(4) Hurwitz, S. H., and Meyer, K. F., Journ. Exper. Med. 24 (1916), p. 



515. 



(5) Jewett, R. M., Journ. Biol. Chem. 25 (1916), p. 21. 



(6) Kober, P. A., Journ. Biol. Chem. 13 (1912), p. 485. 



(7) Kober, P. A., Journ. Amer. Chem. Soc. 35 (1913), p. 290. 



(8) Kober, P. A., Journ. Amer. Chem. Soc. 35 (1913), p. 1585. 



