192 GASTRIC DIGESTION : CHYMIFICATION. 
Chemists, render it probable that this change is of the nature 
of fermentation. : 
210. It is a fact of great practical importance, that a cer- 
tain quantity of the gastric fluid can act only upon a limited 
amount of alimentary matter ; so that, if more food be taken 
into the stomach than the gastric fluid can dissolve, it remains 
there undigested. Now it has been already mentioned, that 
the quantity of the gastric fluid secreted at any one time, is 
proportional, not to the amount of food in the stomach, but 
to the wants of the system ; so that, if more food be swal- 
lowed than is required to repair the waste of the body, it 
lies for some time unchanged in the stomach, and becomes a 
source of irritation which prevents the due discharge of its 
functions ; and the evil goes on increasing with every addi- 
tion to the contents of the cavity. This may not be felé by 
the individual at the time ; but it leaves permanent effects, 
which manifest themselves sooner or later in derangement of 
the general health. The habit of taking more food than is 
really necessary, and of irritating the stomach by stimulating 
substances or fluids (such as pepper, mustard, spirits, &c.), is 
a fertile source of disease. The injurious effects of these are 
manifested by the thirst which is the consequence of their 
use, and which is a call (as it were) on the part of the stomach, 
to prevent their irritating action by diluting them with water, 
211. By the solution of its albuminous portion, and the 
separation of its other component particles, the food is re- 
duced in the stomach to a kind of pulp, which is termed 
chyme. The consistence of this will of course vary accord- 
ing to the nature of the food, and the quantity of fluid in the 
stomach ; but in general it is grayish, semi-fluid, and uniform 
throughout. When the food has been of a rich character, the 
aspect of the chyme resembles that of cream ; but when the 
food has consisted of farinaceous substances (rice, potatoes, 
&c.), the chyme is more like gruel. At the point where the 
stomach opens into the intestinal canal, which is called the 
pylorus, there is a kind of valve, which permits the chyme 
to pass as fast as it is formed, but closes against the portions 
of the food which are yet solid and undigested ; and thus the 
chyme escapes from the stomach in successive waves, slowly 
at first, but afterwards more rapidly, as the digestive process 
approaches its completion. 
