220 THE BODY AT WORK 



capacious reservoirs. It is thanks to their capacity for storing 

 blood that a supply is provided adequate to meet any special 

 demand. If a man runs a few hundred yards, two-thirds of the 

 whole blood of the body is transferred to his limbs. It is 

 quickly withdrawn from the abdominal vessels when it is 

 wanted elsewhere ; but, failing an efficient cause for removing 

 it, its accumulation induces lethargy. Even tight-lacing has 

 been defended by an eminent physiologist on the ground that 

 it prevents accumulation of blood in the abdomen. But tight- 

 lacing diminishes the capacity of the chest, hampers the action 

 of the heart, checks the circulation, distorts the abdominal 

 viscera, and generally deforms and jams the domestic 

 machinery, even though the professor be right in his view that 

 visceral compression may favour alertness of mind. More by 

 token, it interferes with this admirable adjustment by which 

 blood is distributed to the various parts of the body in propor- 

 tion to their needs. The brain is the only organ which has any 

 difficulty in securing all it wants, and its claim to so much blood 

 might be disputed. Nature has not provided for long-con- 

 tinued passivity of the body associated with strained activity of 

 mind. When the stimulus to mental activity is not unreasonable, 

 most " nervous " people are apt to discover that their brains 

 are better supplied with blood than is good for their health. 



The effect upon the distribution of blood throughout the 

 body of squeezing the viscera is experienced after taking a deep 

 breath and contracting the muscles of the abdomen. The 

 contents of the abdomen are compressed between the depressed 

 diaphragm and its muscular wall. 



Certain other forces co-operate with the beat of the heart 

 in causing blood to circulate. Two such factors are especially 

 deserving of attention. In the first place, the movement of 

 blood in veins is largely dependent upon external pressure. 

 The veins are valved at frequent intervals, the folds in their 

 interior being of course directed towards the heart. Any 

 external force which empties a section of a vein drives blood 

 forward. A " good stretch " brings the lateral pressure of 

 contracting muscles to bear upon the walls of the veins which 

 lie between them, or beneath. More blood is delivered to the 

 heart. The exercise of standing erect in the attitude of atten- 

 tion, and then slowly raising the arms until the thumbs meet 



