THE CIRCULATION 57 



function in the body, must work harder than if it were in 

 a normal condition. Rheumatic attacks of the heart do 

 most harm when they occur in early life the period 

 when the valves are the most easily affected. Any ten- 

 dency toward rheumatism in children has, therefore, a 

 serious significance and should receive the attention of the 

 physician. Any one having a defective heart should avoid 

 all forms of exercise that demand great exertion. 



Strengthening of the Blood Vessels. Disturbances of 

 the circulation, causing too much blood to be sent to cer- 

 tain parts of the body and an insufficient amount to others, 

 when resulting from slight causes, are usually due to weak- 

 ness of the walls of the blood vessels, particularly of the 

 muscular coat. Such weakness is frequently indicated by 

 extreme sensitiveness to heat or cold and by a tendency to 

 " catch cold." From a health standpoint the preservation 

 of the normal muscular " tone " of the blood vessels is a 

 problem of great importance. Though the muscles of the 

 blood vessels cannot be exercised in the same manner as 

 the voluntary muscles, they may be called actively into 

 play through all the conditions that induce changes in the 

 blood supply to different parts of the body. The usual 

 forms of physical exercise necessitate such changes and 

 indirectly exercise the muscular coat. The exposure of 

 the body to cold for short intervals, because of the changes 

 in the circulation which this induces, also serves the same 

 purpose. A cold bath taken with proper precautions is 

 beneficial to the circulation of many and so also is a brisk 

 walk on a frosty morning. Both indirectly exercise and 

 strengthen the muscular coat of the blood vessels. On 

 the other hand, too much time spent indoors, especially in 

 overheated rooms, leads to a weakening of the muscular 

 coat and should be avoided. 



