168 



BLOOD AND LYMPH 



they are so necessary to the life of man it is evident that there 

 must be a constant renewal of the supply from some source. This 

 source is found in the red marrow of bones. Here are produced 

 nucleated, colorless cells, called erythroblasts, which multiply 

 and form daughter cells. These daughter cells finally produce 

 haemoglobin in their cytoplasm, and thus form nucleated red 

 corpuscles. These lose their nucleus and finally enter the blood 

 stream in the form we have recognized as red corpuscles. The 

 old corpuscles are continually breaking down, and after undergoing 

 dissolution in the blood stream, the liberated haemoglobin is 

 discharged by the liver as bile pigment. It was once thought 

 that their destruction took place in the spleen, but there is no 

 evidence to prove this and it is now believed that this destruction 

 may take place anywhere in the blood stream. In a normal 

 human being the supply and loss is so balanced as to 'maintain a 

 fairly constant number of corpuscles in the blood. 



The number of red corpuscles in the blood varies not only with 

 the sexes, as already noted (see p. 165), but also with other con- 

 ditions. They increase greatly with the altitude, supposedly to 

 compensate for the reduction in air supply. They often decrease 

 in number in disease causing a condition known as anemia. At 

 present the remedies for lack of blood corpuscles usually take 

 the form of tonics, that is, the giving of medicines, usually rich 

 in iron, which stimulate the formation of both erythroblasts and 

 haemoglobin. Exercise in the open air is a far better remedy than 

 any drug for this condition. 



"White Corpuscles. — These bodies are not nearly so num- 

 erous as the red corpuscles being only five thousand to 

 seven thousand per cubic millimeter. They are colorless 

 amoeboid cells having a nucleus and no definite cell out- 

 line, moving about in the plasma in much the same man- 

 ner as an amosba, which thc^y strongly resemble. They 

 are of two kinds: those with granular cytoplasm are more 

 numerous and are called leucocytes ; those without granules 

 in the cytoplasm are called lymphocytes. The leucocytes 



