THE BLOOD 



245 



standing these slight differences, all forms belong to the same crystal system, 

 with the exception of those from the squirrel. 



A simple but very effective method of obtaining blood-crystals suggested 

 by Reichert is to lake defibrinated blood, especially that of the dog, rat, 

 guinea-pig, and horse, with acetic or ethylic ether and then add a solution, 

 i to 5 per cent., of ammonium oxalate. A drop of this mixture placed under 

 the microscope will show crystal formation in a very few minutes. 



Chemic Composition of Hemoglobin. By appropriate methods 

 hemoglobin can be obtained in a practically pure form, and when subjected 

 to a temperature of iooC. its water of crystallization is driven off, after 

 which it can be analyzed. In the subjoined table the results of several 

 analyses are given for 100 parts of hemoglobin. 



The percentage composition of hemoglobin is thus seen to vary slightly 

 in different animals, suggesting that there may be different kinds of hemo- 

 globin. The molecular composition is not known. On the assumption 

 that each molecule contains one atom of iron, Preyer suggested the following 

 empirical formula: C 600 H 960 N l54 O 179 S3Fe, with a molecular weight of 

 i3>33 2 ; Jaquet has suggested a different formula: C 758 H 1203 N 195 O 218 S 3 Fe, 

 with a molecular weight of 16,669. It is Ver 7 evident from this that the 

 molecule is of enormous size and exceedingly complex. 



Quantity of Hemoglobin. The quantity of hemoglobin in blood as 

 determined by chemic, chromometric, and spectro-photometric methods 

 amounts to about 14 per cent, in man and 13 per cent, in woman. Of the 

 chemic methods, that based on the amount of iron in the blood is the one 

 generally employed. Chemic analysis has shown that hemoglobin 

 contains 0.33 per cent, and blood 0.046 per cent, of iron; with these two 

 factors the percentage of hemoglobin can be determined by the following 



formula: x= = 14 per cent. The total quantity of hemo- 



- oo 



globin in the blood, assuming the latter to be about 3684 grams (one- 

 nineteenth of the body-weight, 70 kilos) will therefore amount to 515 



grams; e.g., x=- - = 515. The total amount of iron in the blood 



100 



is obtained by the following formula: viz., x- : 1.70 grams. 



100 



Clinic Methods for the Determination of the Percentage of Hemo- 

 globin. Under normal physiologic conditions the percentage of hemo- 

 globin undergoes but slight variation. In pathologic states there is fre- 



