BIOLOGY APPLIED TO HEALTHFUL LIVING 535 



to low temperature, thus tending to avoid the dangerous 

 internal congestions known as " colds." It should be noted 

 that " colds " are not confined to the lungs and respiratory 

 passages, for one may have an unrecognized " cold " from 

 congestion of blood in other organs, especially in stomach, 

 intestine, and kidneys. 



If in spite of systematic cold bathing one's skin some- 

 times gets so chilled that it does not soon react, the normal 

 circulation should be restored by ways suggested in 453. 

 To allow the skin to remain chilled for hours is dangerous. 



Cold baths are best taken before breakfast, never within 

 two hours after a meal, because the rush of blood to the skin 

 interferes with the proper supply in the digestive organs. 



NERVOUS SYSTEM 



459. Overwork. Unhealthy conditions of the nervous 

 system are frequently the result of overwork, both mental and 

 physical. Hence it is important that brain-workers should 

 consider the hygiene of the nervous organs. 



Regular mental work, as well as physical work, should be 

 limited to a number of hours per day ; and these should be 

 the hours before late in the afternoon, when the maximum 

 exhaustion of nervous force occurs. Nervous exhaustion 

 from mental overwork is most often due to neglect of this 

 rule; and the brain-worker should limit his regular day's 

 work to a reasonable number of hours per day, and those 

 when the brain is at its best. Too often mental overwork 

 simply means such long days at intellectual tasks that exercise, 

 recreation, and sleep are neglected. Sooner or later, this 

 means the inevitable penalty of nervous disturbance, if not 

 serious breakdown. 



There come times in the lives of many brain-workers when 

 some important work demands temporary nervous strain; 

 but the man who is wise in the laws of hygiene will try to re- 



