ON POSTURE AND ITS INDICATIONS. 31 



advantage in cases of severe and persistent headache, where other 

 remedies fail to relieve. Even where such a strong irritant as 

 snuff is not resorted to, smelling salts (sal volatile) or aromatic 

 vinegar may give considerable relief in headache if frequently 

 inhaled. 



While stimulation of the fifth nerve as just described tends to 

 keep people awake and increase their mental activity, gentle, 

 rhythmical stroking of the head tends, on the contrary, to make 

 them fall asleep, and brushing the hair has this effect on many 

 people to such an extent that the movements of the hair-dresser's 

 fingers over the scalp, and rhythmical click of the shears, will 



Fig. 13. Fio. 14. 



send some people to sleep, even at the risk of having their hair 

 shorn to a much greater extent than would be at all pleasing to 

 them on awakening. A gentle rubbing of the scalp, as if to 

 loosen it upon the skull, also tends not only to soothe irritability, 

 but to relieve and to prevent headaches. 



External temperature has a powerful effect in determining 

 posture. On a hot summer's day the natural tendency is to lie 

 down with the head slightly raised, the arms hanging loose, and 

 one leg extended, while the other perhaps is drawn up, as in Fig. 

 13. The physiological reason for this posture is that in it the 

 greatest extent of cooling is attained, for it insures the greatest 

 possible exposure of the largest vascular district in the body — 

 viz., the intestinal vessels — to the cooling influence of the exter- 

 nal air. This is aided by the loss of heat due to the evaporation 

 of sweat. By the slight raising of the head and the drawing up 

 of one leg, the abdominal parietes are rendered loose, and the 

 intestines tend to fall sideways, and the abdomen tends to become 

 flattened from before backward. The greatest extent of cooling 

 surface is thus obtained, and the temperature of the body is kept 

 as low as possible. 



An entirely opposite attitude is assumed when the external air 

 is cold (Fig. 14). The thin abdominal walls being insufficient to 

 protect the intestinal vessels from the cooling influence of the 

 external air, the legs are drawn up until the thick muscles of the 

 thigh form a warm covering to the abdomen and thus prevent 



