BLOOD AS A TISSUE 147 



to be able to assimilate it better. Whether the liver diet is reme- 

 dial because of the iron present, or whether there is a vitamin 

 present that stimulates the body to make more red corpuscles, 

 has not yet been conclusively proved. In order to determine 

 whether a person has anaemia, a drop of blood is put on a slide 

 which is divided into sections by marks etched on the surface. 

 These spaces are called counting chambers. The number of red 

 corpuscles are estimated in relation to the white corpuscles present. 

 This is called a blood count. If there are too few red corpuscles 

 in relation to the white corpuscles, the person is said to be anaemic. 

 There is also a color scale used to test for anaemia. 



The haemoglobin in the red corpuscles readily unites with oxy- 

 gen and forms an unstable compound, oxyhaemoglobin. When 

 the oxygen-carriers pass cells deficient in oxygen, the oxyhaemo- 

 globin will give up its oxygen supply. The red corpuscles of man 

 are smaller than the red corpuscles of nearly every other animal. 

 This allows a greater number per given volume and gives a greater 

 absorbing surface. Thus these numerous small corpuscles carry a 

 greater supply of oxygen than if they were larger. 



The white corpuscles are larger and less numerous than the red 

 corpuscles. Because they are capable of independent motion, 

 they can force their way among the cells, which make up the walls 

 of capillaries, and escape into surrounding tissues. Certain of the 

 white corpuscles, by means of their protoplasmic processes, en- 



--..,- ..- l_/v 



White corpuscles can make their way among the cells in the walls of capillaries by their inde- 

 pendent motion. They may be found in tissues where they can attack invading bacteria. 



gulf the bacteria in blood and other tissues, and digest them. 

 These are the phagocytes and the process is phagocytosis. It is 

 thought that white corpuscles originate in lymph nodes and in the 



