. SENSE OF HUNGER—SECRETION OF GASTRIC JuIcE. 189 
. in abundance when the lining membrane is stimulated by 
the contact of food, especially solid food. Only a limited 
quantity is secreted at any one time ; and this quantity is 
just that which is sufficient to dissolve food enough for the 
supply of the natural wants of the system. The contact of 
' any solid substances with the interior of the stomach, is suffi- 
cient to produce a flow of this fluid into its cavity ; but the 
secretion soon ceases if the substance be not of an alimentary 
nature, 
_ 205. The sense of hunger appears due to the distension of 
the blood-vessels of the stomach, which takes place in pre- 
paration for the secretion of the gastric fluid. This deter- 
mination of blood towards the stomach seems to occur when- 
‘ever the body needs a fresh supply of nourishment ; and it 
_ ceases as soon as a sufficient amount of gastric fiuid has been 
drawn off. Hence it is, that hunger is relieved by eating ; 
and hence it is, also, that hunger is for a time relieved by 
taking solid substances into the stomach, even though they 
contain no nourishing matter. It is from having experienced 
this, that savage nations are in the habit of mixing indiges- 
tible solid matter with the fiuids that sometimes constitute 
_ their principal articles of food. Thus the Kamschatdales mix 
earth or saw-dust with the train-oil on which alone they are 
frequently reduced to live ; and the Veddahs, or wild hunters 
_ of Ceylon, mix the pounded fibres of soft or decayed wood 
with the honey on which they feed when meat is not to be 
had. One of them being asked the reason of the practice, 
replied, “ I cannot tell you, but I know that the belly must 
be filled.” It has been found by experiment, that soups and 
_other forms of liquid aliment are not alone fit for the support 
of the system, even though they may contain a large amount 
of nutritious matter ; and the medical man well knows, that 
_™many persons have stomachs too weak and irritable to retain 
_“slops” (as they are commonly termed), who can yet digest 
solid food of a simple kind. All these instances show, that 
the contact of a.solid substance with the walls of the stomach, 
is the proper stimulus or excitement to the secretion of the 
£astri ul 
206. This fluid, when poured upon the food, is thoroughl 
‘mixed-up with it by a peculiar movement of the walls of the 
‘Stomach, which is continually bringing fresh portions of the 
