396 LIQUID PARTS OF ANIMALS. 



cavity. It is never accumulated in the cavity of the fasting sto- 

 mach, and is seldom or never discharged, except when the ves- 

 sels secreting it are excited by the natural stimulus of food, by 

 mechanical irritation of tubes, or by other excitements. When 

 food is received, the juice is given out in exact proportion to its 

 acquirements for solution, except when more food has been taken 

 than is necessary for the wants of the system. 



Probably the secretion from mechanical irritation is less than 

 that produced by the stimulus of food : the latter is diffused over 

 the whole villous coat, while the former is only partial. On 

 viewing the interior of the stomach, the peculiar formation of its 

 inner coats is distinctly seen. When empty, the rugae appear 

 irregularly folded on each other, almost quiescent, of a pale pink 

 colour, and lubricated with mucus. On the application of food, 

 the action of the vessels is increased, the colour brightened, and 

 the vermicular motion excited. The small gastric papillae begin 

 to discharge a clear transparent fluid, which continues to accu- 

 mulate abundantly as the food is received for digestion. 



If the mucous covering of the villous coat be wiped off with a 

 sponge during the period of chymification, the membrane ap- 

 pears roughish, at first of a deep pink colour, but in a few se- 

 conds the follicles and fine papillae begin to pour out their re- 

 spective fluids, which, being diffused over the parts abraded of 

 mucus, restore to them their peculiar soft and velvety appear- 

 ance and pale pink colour ; and the gastric juice increases and 

 trickles again down the sides of the stomach. 



If the mucus be wiped off when the stomach is empty, a simi- 

 lar roughness and deep colour appear, though less in degree, and 

 the mucus is more slowly restored. The follicles swell more gra- 

 dually, and the fluids do not appear in such quantities as to 

 trickle down, the mucus alone being restored. 



In disease, the inner membrane of the stomach presents vari- 

 ous and essentially different appearances. In fever, obstructed 

 perspiration, undue excitement by spirituous liquors, or when 

 overloaded with food, while under the influence of fear, anger, 

 or whatever depresses or disturbs the nervous system the villous 

 coat becomes sometimes red and dry, at other times pale and 

 moist, and loses its smooth and healthy appearance. The secre- 

 tions become vitiated, greatly diminished, or entirely suppressed. 



The mucous covering can scarce be observed ; the follicles are 



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