220 ORGANIC AGRICULTURAL CHEMISTRY 



facts in regard to the nature and properties of the more promi- 

 nent of the two, viz. the blood. 



Properties. — The blood of mature animals is an opaque, 

 dark red fluid with a neutral reaction according to the concen- 

 tration of hydrogen and hydroxyl ions, but an alkaline reaction 

 as ordinarily tested with litmus paper, due to the presence of 

 sodium carbonate and phosphate. In man it has a specific 

 gravity of 1.06 and the amount in the body equals about 7.5 

 per cent of the body weight. 



Constituents 



The constituents of the blood are of two kinds, viz. organic 

 and inorganic. These are present in two conditions, viz. either 

 in true solution or in suspension in the liquid substratum, water. 

 The liquid portion of the blood, including both the solvent and 

 those substances in true solution, is known as hlood plasma. In 

 this plasma the suspended substances are held. 



The material held in suspension in blood plasma amounts to 

 about 60 per cent of the blood and consists of cellular bodies 

 known as blood corpuscles, blood plates and blood dust. The 

 most important of these bodies are the two forms of corpuscles 

 known as red corpuscles or erythrocytes and white corpuscles or 

 leucocytes. 



Red Blood Corpuscles or Erythrocytes. — The erythrocytes 

 are cells which have lost their nucleus. In mammals they have 

 the microscopical appearance of biconcave disks. They are of 

 a yellowish color but in masses appear red. Their color is due 

 to a protein known as hcemoglohin which permeates the real cell 

 material known as the stroma. The stroma constitutes only 

 5 to 10 per cent of the dry matter of the corpuscles, while 90 

 to 95 per cent consists of haemoglobin. Two important con- 

 stituents of the stroma are lecithin and cholesterol, which will be 

 considered later (p. 280). 



Haemolysis and HaBmagglutination. — Two properties of 

 erythrocytes are of especial importance in connection with the 

 action of toxins and the condition of immunity. When the 



