HEMOGLOBIN 



119 



tents. In some the formation of crystals is almost spontaneous, whereas 

 in others it takes place either with great difficulty or not at all. Among 

 the animals whose blood coloring-matter crystallizes most readily are the 

 guinea-pig, rat, squirrel, and dog; and in these cases to obtain crystals it 

 is generally sufficient to dilute a drop of recently drawn blood with water 



FIG. 119. Crystals of Oxyhemoglobin Prismatic, from Human Blood. 



and to expose it for a few minutes to the air. In many instances other means 

 must be adopted, e.g., the addition of alcohol, ether, or chloroform, rapid 

 freezing, and then thawing, the application of an electric current, a tempera- 



FIG. 120. Oxyhemoglobin Crystals Tetrahedral, from Blood of the Guinea-pig. 



ture of 60 C., the addition of sodium sulphate, or the addition of decom- 

 posing serum of another animal. 



.The hemoglobin of human blood crystallizes with difficulty, as does also 

 that of the ox, the pig, the sheep, and the rabbit. 



