COMPOSITION OF THE BLOOD 145 



II. Suggest a reason for calling the white corpuscles the amoeboid cor- 

 puscles ? 



III. State three structural differences between the red and white corpuscles. 



IV. What functions did the Amoeba perform with its pseudopodia ? Cer- 

 tain white corpuscles can, in a similar manner, engulf bacteria. These bac- 

 teria are then digested by the white corpuscles and are thus eliminated from 

 the blood. 



Composition of the blood. Blood may be called a tissue. 

 It consists of a yellowish liquid, the plasma, and cellular particles, 

 the red and white corpuscles and blood platelets. The plasma 

 is a clear fluid containing fibrinogen and other blood proteins, 

 nutrients, and wastes. Some of the proteins in the plasma are 

 peculiar only to the blood. Little is known of the use of these, 

 with the exception of fibrinogen. The use of fibrinogen, which was 

 transformed to fibrin in our laboratory exercises, will be discussed 

 later. Amino-acids are also a part of the blood plasma. These 

 amino-acids are digested proteins which are called building stones 

 of the body. They are distributed by the blood to the cells, and 

 they build protoplasm. Fat, glucose, water, and mineral matters 

 are also taken in by the plasma from the alimentary canal. More 

 than 80 per cent of the plasma is water. There is from 0.07 to 0.15 

 per cent each of fat and glucose. The proteins constitute from 

 6 to 8 per cent of the plasma. 



All of the food that is digested and absorbed does not circulate. 

 It is either used or stored in cells and gradually returned to the 

 blood as tissue cells require it. Animal cells can store fat and 

 starch, but very little protein. Therefore, any extra protein eaten 

 tends to be broken down and eliminated. Secretions from ductless 

 glands are absorbed directly into the blood. These liquids circulate 

 through the body, activating, inhibiting, or regulating the more 

 remote parts. 



Oxygen is taken from the lungs by the red corpuscles of the 

 blood. The wastes, carbon dioxide, water, and urea, collected from 



