SECTION X 

 THE ABSORPTION OF THE FOOD-STUFFS 



THE ABSORPTION OF WATER AND SALTS 



THE intake of water, and probably of salts, by the alimentary canal, in 

 accordance with the requirements of the organism as a whole, seems to 

 be regulated almost entirely by the central nervous system, the higher parts 

 of this system, viz. those concerned with appetite, being particularly in- 

 volved in the process. Thus in man any large loss of fluid to the body, as by 

 sweating, diarrhoea, haemorrhage, gives rise to an intense thirst that has its 

 natural reaction in increased intake of water by the mouth. On the other 

 hand, the property possessed by the alimentary canal of absorbing water and 

 weak saline fluids contained in its interior is very little influenced by the 

 state of depletion, or otherwise, of the water depots of the body. It is 

 practically impossible, however large the quantities of fluid ingested, to 

 evoke the production of fluid motions, the greater part of the ingested 

 fluid being absorbed on its way through the alimentary canal. Thus a 

 man may keep himself in perfect health and maintain the water content of 

 his body constant whether he take one litre or six litres of water daily. The 

 whole process of regulation, apart from that determined by appetite, is 

 carried out at the other end of the cycle, viz. by the kidneys. As concerns 

 absorption of water there is no chemical solidarity between the alimentary 

 surface and the rest of the body. Whenever water, is presented to the 

 surface it is absorbed and passes into the circulation. 



The absorption of water in the stomach may be regarded as nil. 

 Although from this viscus alcohol, and possibly peptone and sugar, may 

 be absorbed to a slight extent, water or saline fluids introduced into it 

 are passed through the pylorus either without change or increased by the 

 secretion of fluid from the gastric glands. In no case is there a diminution 

 of fluid in the stomach. 



The chief absorption of water occurs in the small intestine. It is on 

 this account that the salient features of cases of dilatation of the stomach 

 with stenosis, absolute or relative, of the pyloric orifice can be nearly all 

 referred to the starvation of the body in water, and can be often relieved 

 by the administration of water either subcutaneously or by the rectum, i.e. 

 by the channels through which absorption is still possible. The introduction 

 of water into the stomach simply increases the dilatation, but does not 

 relieve the intense thirst of the patient. Water that has been swallowed 



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