The Physiological Basis oj Thirst. 



301 



I am aware that many questions arising from the views which I have just 

 developed remain to he solved — questions as to the effects which other 

 glandular activity, removing fluid from the body, may exercise on the 

 functions of the salivary glands ; the alteration of properties of the blood and 

 lymph other than osmotic pressure as affecting secretion; the relation 

 between the so-called " free water " of the body fluids and salivary secretion 

 when water is withheld ; the influence of strong alcoholic beverages in pro- 

 ducing thirst ; and the nature of pathological states in which thirst seems to 

 disappear. But these and other pertinent questions must await more peaceful 

 times for their answers. 



From the evidence presented, however, it seems to me that we are now in 

 a position to understand the mechanisms by which all three of the essential 

 supplies from the outer world are provided for in our bodily economy. The 

 oxygen supply is arranged for by the control which changes in the blood, 

 brought about mainly by variations in the carbon dioxide content, exert on 

 the centre for respiration. The proper food supply ultimately is assured, 

 because we avoid, or check, by taking food, the distressing pangs of hunger 

 which powerful contractions of the empty stomach induce unless food is 

 taken. And the water supply is maintained because we avoid, or abolish, by 

 taking water or aqueous fluid, the disagreeable sensations which arise and 

 torment us with increasing torment if the sahvary glands, because of a 

 lowering of the water- content of the body, lack the water they need to 

 function, and fail therefore to pour out their watery secretion in sufficient 

 amount and in proper quality to keep moist the mouth and pharynx. 



VOL. XC. — B. 



