314 THE CHEMISTRY OF ANIMAL PHYSIOLOGY 



apparently a function of the iron, one atom of iron combining 

 with two atoms of oxygen. The oxygen can be removed by 

 means of reducing agents, by merely passing a neutral gas 

 like nitrogen through a solution containing haemoglobin, or 

 by exposure to a vacuum. Haemoglobin is darker red, more 

 purplish in color, than is oxyhemoglobin, which is bright 

 red. Blood which flows in the veins is darker in color than 

 that which flows in the arteries, there being more haemoglobin 

 in the veins and more oxyhemoglobin in the arteries. Haemo- 

 globin in the form of oxyhaemoglobin is the oxygen carrier 

 of the blood. As was noted above, carbon monoxide will 



Fig. 78. — Human red blood corpuscles. Highly magnified, a, seen from 

 the surface; b, seen in profile and forming rouleaux ; c, rendered spherical 

 by water; d, rendered crenate by salt solution. (Gray.) 



unite with haemoglobin and the combination is stronger than 

 the combination of oxygen with haemoglobin. Hence in an 

 atmosphere containing carbon monoxide, the oxygen is 

 driven out of combination with the haemoglobin and the 

 carbon monoxide takes its place. This is the cause of carbon 

 monoxide poisoning, since the carrying of oxygen by the 

 haemoglobin is a very necessary function of the blood. 



(c) White Corpuscles, Leucocytes, occur in the blood 

 of man to the extent of about 5000 to 10,000 to the cubic 

 millimeter. They are more variable in size and form than 

 the red corpuscles, being 4 to 13 microns in diameter (0.004 

 to 0.013 mm.). They can move by their own processes, 



