& 



THE INTERNAL MEDIUM. 47 



sumes its proper form when the external force is removed. 

 The corpuscles are, then, highly elastic; they frequently can 

 be seen much dragged out of shape inside the vessels when 

 the circulation of the blood is watched in a living animal 

 (Chap. XV), but immediately springing back to their normal 

 form when they get a chance. 



Blood-crystals. Haemoglobin is, as above shown, readily 

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

 warm room, breaking up into a colorless proteid substance 

 called globulin and a red body, Jicematin. By keeping the 

 haemoglobin solution very cold, however, this decomposition, 

 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 



j ^~ z^a . fourth of its volume of 



% ^r f ^ - cold alcohol added to it 

 iP^ rd^ ^H and the mixture be put in, 

 ^0^ <|j a refrigerator for twenty- 



S^"~ 3 ^ittK f U1 ' hours, a part of the 

 haemoglobin will often 

 crystallize out and sink to 

 the bottom of the vessel, 



FIG. 14,-Biood.crystais, or haemoglobin where it can be collected for 

 crystals, examination. The haemo- 



globin of the rat is less soluble than that of man, and there- 

 fore crystallizes out especially easily; but these haemoglobin 

 crystals, or, as they are often called, blood-crystals, can also 

 be obtained from human blood. In 100 parts of dry human 

 red blood-corpuscles there aro of 90 haemoglobin. The haemo- 

 globin is the essential constituent of the red blood-corpuscles, 

 enabling them to pick up Targe quantities of oxygen in the 

 lungs and carry it to other parts. (See Respiration.) 



Haemoglobin contains a considerable quantity of iron, much, 

 more than any other proximate constituent of the Body. 



The Colorless Blood -corpuscles (Fig. 13, F, H, G). The 

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

 numerous thai: the red; in health there is on the average 

 about one white to three hundred red, but the proportion 

 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. 



