OXYH^MOGLOBIN. 239 



The color of the crystals and their solution vary according to 

 the light by which they are looked at. By reflected light they 

 are bluish-red or greenish in color, and by direct light scarlet. 



The preparation of oxy haemoglobin crystals is accomplished by 

 first separating the coloring matter from the corpuscles by freez- 

 ing, or the addition of water or ether, and rendering it less 

 soluble by evaporation, cold, and the addition of alcohol. 



For microscopic observation it generally suffices to kill a rat 

 with ether, and expose a drop of the blood diluted with distilled 

 water on a slide until half dried, and then cover. Crystals 

 appear in the fluid as it becomes more concentrated. 



FIG. 106. 



Crystals of Haemoglobin from different animals, showing the variety in form of crystals 

 1, man; 2, guinea pig; 3, squirrel. 



The combinations which haemoglobin enters into are numerous, 

 and throw much light upon the function of the corpuscles. 



As already stated, the coloring matter, when exposed to the 

 air, combines with oxygen to form a loose chemical compound 

 called oxyhaemoglobin. This is the condition in which the col- 

 oring matter of the blood is commonly met with. Although so 

 prone to combine with oxygen, the oxyhaemoglobin very readily 

 parts with some of it. In the circulation it is always united with 

 oxygen, normally leaving the lungs in a state of saturation. On 

 its way through the capillaries of the tissues it parts with some of 

 its oxygen, becoming more or less reduced (haemoglobin), but 

 even the most venous blood always contains some oxy haemoglobin. 



The oxygen can be removed by reducing the pressure under an 



