190 PHYSIOLOGY. 



up the oxygen. Oxyhemoglobin, minus oxygen, is usually termed 

 reduced haemoglobin; better, however, simply haemoglobin. Oxy- 

 haemoglobin is most abundant in arterial blood; that is, blood that 

 has received its oxygen from the lungs during respiration and is 

 then on its way to supply the needs of the cells of the tissues. Oxy- 

 hemoglobin behaves as an acid. Ordinary venous blood, upon expo- 

 sure to the air for a considerable length of time, becomes bright red 

 because of the union of the oxygen of the air with the hemoglobin 

 of the blood. 



Crystallization of Haemoglobin. The haemoglobin is contained 

 within the stroma of the corpuscles. In form, the crystals of the 

 blood of man and of the great majority of animals are that of 



Fig. 56. Teichmann's Haemin-crystals. (LAHOUSSE.) 



rhombic prisms or needles which belong to the rhombic system; in 

 the squirrel they are six-sided plates. 



Hemoglobin crystals are readily broken up by the addition of 

 an acid or an alkali into two parts : licematin and globin. Hcematin 

 is a brown pigment, representing the cleavage product of hemoglobin 

 in the presence of oxygen. It contains all of the iron of the decom- 

 posed crytals, and is not crystallizable. In addition to the iron, it 

 contains the four chief elements of proteid bodies : carbon, hydrogen, 

 oxygen, and nitrogen. Globin is the proteid element of the hemo- 

 globin. It contains all the sulphur, and constitutes the major pro- 

 portion of the hemoglobin molecule, which is 16,000 times heavier 

 than a molecule of hydrogen. 



The stroma of the red corpuscles is as 1 to 12 to the quantity 

 of hemoglobin. The whole quantity of blood of a man of medium 

 weight holds about 680 grams of hemoglobin. E. T. Eeichert pre- 

 pares blood-crystals by laking defibrinated blood, of a dog or guinea- 

 pig, with acetic or ethylic ether, and then adding a solution of 1 to 



