CHEMICAL EXAMINATION OF THE BLOOD. 351 



latter is precipitated in its coagulated state. From its solutions 

 the substance is thrown down by half-saturation with ammonium 

 sulphate. On reduction with ammonium sulphide, with Stokes' 

 reagent, or during the process of putrefaction, it is transformed 

 into haemoglobin. Other reducing agents, such as sodium hydro- 

 sulphite, give rise to the formation of so-called pseud ohemoglobin, 

 which apparently stands midway between oxyhsemoglobin and 

 haemoglobin in containing less oxygen than the former, but more 

 than the latter. Its spectrum, however, is the same as that of the 

 completely reduced haemoglobin. 



In sufficiently dilute solution oxyhemoglobin shows two bands 

 of absorption between D and E. The one to the left, which is not 

 so wide as the other, but darker and more sharply denned, borders 

 on D, while the second lies at E. 



The Quantitative Estimation of Oxyhaemoglobin. This is best 

 accomplished by Hoppe-Seyler's method, which is based upon 

 the comparison of a given amount of diluted blood with a stand- 

 ard solution of crystallized oxyhsemoglobin. This solution is 

 prepared by dissolving 2 grammes of the pure coloring-matter in 

 50 c.c. of distilled water. The oxyhemoglobin is then transformed 

 into carbon monoxide hemoglobin by passing a current of the gas 

 through the solution to saturation. It is then stored in drawn- 

 out and sealed glass tubes, such that each tube contains about 

 6 c.c. The contents of each tube, when diluted with ten times its 

 volume of water, will then represent a 0.2 per cent, solution of the 

 oxy hemoglobin. 



A carefully measured or weighed amount of blood, not exceed- 

 ing 0.5 c.c., is now diluted with water that has been saturated with 

 carbon monoxide to exactly 5 c.c. A small drop of a very dilute 

 solution of sodium hydrate is added if necessary to remove any 

 turbidity that may exist. This solution is further saturated with car- 

 bon monoxide, and freed from fibrin by filtration. The filtrate should 

 measure exactly 4 c.c. The comparison of the two solutions, and 

 the further dilution of the blood with carbon monoxide water then 

 takes place in the so-called double pipette of Hoppe-Seyler. The 

 color of the two solutions is here equalized, and the amount of 

 hemoglobin present in the specimen of blood calculated from the 

 degree of dilution. 



Example.- Suppose that we started with 0.5 gramme of blood, and 

 that the standard solution contained 0.002 gramme of oxyhemoglo- 

 bin in the cubic centimeter. The 4 c.c. of the diluted and filtered blood 

 are further diluted in the pipette to 22 c.c , which corresponds to a 

 total solution of 27.5 c.c. for the total 5 c.c. of the first dilution. In 

 these 27.5 c.c., which represent the original 0.5 gramme of blood, 

 there will consequently be 27.5 X 0.002 = 0.0550 gramme of 

 hemoglobin. The percentage will accordingly be 11 per cent. 



In the clinical laboratory other forms of apparatus are in use, 

 such as the hcemometers of Dare and Fleischl, and the haemoglobin- 



