THE BLOOD 349 



essential. Sleep also seems to be a necessary factor in the health 

 of the red corpuscle. Many are familiar with the pale face 

 which comes from sleeplessness and overwork in poorly ventilated 

 rooms. Moderate exercise is another important factor. The 

 disease called anaemia, which means a lack of red corpuscles in 

 the blood, is too often brought about by sedentary habits and 

 lack of sleep and air. Tonics containing iron are given in such 

 cases so as to supply the lacking element to the haemoglobin of the 

 red corpuscle. 



