BLOOD-CRYSTALS. 47 



soluble in water. In this it soon decomposes if kept in a 

 warm room, breaking up into a proteid substance called 

 globulin and a red-colored body, hamatin. By keeping 

 the haemoglobin solution very cold, however, this decompo- 

 sition can be greatly retarded, and at the same time the 

 solubility of the haemoglobin in the water much diminished. 

 In dilute alcohol haemoglobin is still less soluble, and so if 

 its ice-cold watery solution have one fourth of its volume 

 of cold alcohol added to it and the mixture be put in a re- 

 frigerator for twenty-four hours, a part of the haemoglobin 

 will often crystallize out and sink to the bottom of the 

 vessel, where it can be collected for examination. The 

 haemoglobin of the rat is 

 less soluble than that of 

 man, and therefore crys- 

 tallizes out especially 

 easily; but these haemo-- 

 globin crystals, or, as 

 they are often called, 

 blood-crystals, can also 

 be obtained from human 

 blood. In 100 parts of FIG ^^ . ciystalS; OI T heinoglobin 

 dry human red blood- crystals. 



corpuscles there are 90 of haemoglobin. The haemoglobin 

 is the essential constituent of the red blood corpuscles, 

 enabling them to pick up large quantities of oxygen in 

 the lungs and carry it to all parts of the Body. (See Ees- 

 piration. ) 



Haemoglobin contains a considerable quantity of iron, 

 much more than any other proximate constituent of the 

 Body. 



The Colorless Blood Corpuscles (Fig. 10, F, If, G). 

 The colorless, pale, or white corpuscles of the blood are far 

 less numerous than the red; in health there is on the ave- 

 rage about one white to three hundred red, but the pro- 

 portion may vary considerably. Each is finely granular 

 and consists of a soft mass of protoplasm enveloped in no 

 definite cell-wall, but containing a nucleus. The granules 

 in the protoplasm commonly hide the nucleus in a fresh 



