534 APPLIED BIOLOGY 



a week should be followed by cold water, which causes 

 contraction of the blood-vessels and a subsequent reaction 

 ( 414). 



As far as is consistent with cleanliness, soap with cold water, 

 and especially cold water without soap should be used daily 

 on all parts of the body not exposed. The special reason 

 for cold instead of warm water is given in the next para- 

 graph. 



458. Bathing as a Skin Tonic. Above we have considered 

 bathing for cleanliness only ; but here we are interested in 

 bathing for health. While only in removing bacteria does 

 skin cleanliness appear to be necessary for health, we have 

 fortunately a very strong argument for daily bathing as a 

 means of leading to healthy action of the skin blood-vessels, 

 and indirectly of the whole body. For this purpose water 

 should be much colder than the temperature of the body, 

 and is best applied as sponge-bath, shower-bath, or plunge- 

 bath (as in sea-bathing). Contact with the cold water first 

 causes a reflex action leading to a reduced caliber of the skin 

 arteries, and the skin quickly becomes pallid. A reaction 

 follows brief exposure to the cold water, and the blood-vessels 

 expand, the skin glows, and the bather feels stimulated. No 

 such good effect comes from too long exposure, or when the 

 water is too cold for some people. 



The explanation of the value of this cold bathing is that 

 it gives the skin practice in readjusting its blood-supply when 

 exposed to a low temperature. Many persons, especially 

 those of sedentary habits, have skins which are not accustomed 

 to react quickly to changes of temperature; and hence if 

 chilled their skin arteries remain contracted, blood which 

 ought to circulate in the skin is congested in some internal 

 organ, where inflammation develops, and a " cold " follows. 

 Frequent practice in readjusting the blood-vessels, as given 

 by cold bathing, will make the skin more likely to react and 

 continue to receive its fair share of blood whenever exposed 



