CIRCULATORY SYSTEM. 



121 



ter how old the clot or stain is. Dry blood and salt, 

 equal parts, are ground together on a glass slide, a 

 few drops of glacial acetic acid are added and heat 

 applied until gas-bubbles appear. The crystals are 

 brown, rhombic, and easily recognized. 



Fig. 85. Crystallized hemoglobin: a, b, Crystals from venous blood 

 of man; c, from the blood of a cat; d, from the blood of a guinea-pig; 

 e, from the blood of a hamster; /, from the blood of a squirrel (after 

 Frey). 



MARROW. 



Bone marrow is either white or red. The white 

 marrow occupies the shaft of the bone and is largely 

 fat. The red is found in the ends of bones or can- 

 cellated portions and is richly supplied with blood. 



