LESSON 60.] THE GASTRIC JUICE AND MUCUS. 209 



cited capillary surface, at once represses this circulation and drives 

 it back to its former channels. The blood has been summoned to 

 the stomach, at the time it is specially needed, to supply the neces- 

 sary pabulum for the secretion of mucus and gastric juice> neither 

 of which is kept " on service." Once driven back, what is to be- 

 come of the food, how is it to be digested, when the material for 

 preparing the solvents for it has been sent away ? 



907. "Water containing much lime in solution is altogether unfit 

 to drink, because dangerous. This earth is eliminated by the kid- 

 neys, and passed in the solid form to the bladder, where it concretes, 

 and forms calculi, which can only be removed by the most painful 

 and dangerous operation known to surgery. 



908. Boiling such water has the effect of precipitating the great 

 excess of lime, but too much remains to render it desirable to use, if 

 it can be avoided. For comfort sake, and to have perfect immunity 

 from thirst, the less people drink of any thing the better ; a moderate 

 quantity (two cups) at breakfast, and the like at tea, are all that 

 nature requires, and any one can soon become accustomed to this 

 kind of moderation, by which the soundness of the stomach and the 

 general health will be greatly promoted. Such persons are never dys- 

 peptic, and never know the sensation of thirst, under any circumstances* 



909. The tubes which secrete the mucus lie in the submucous 

 (sub, under, beneath) tissue of the stomach; they are surrounded by 

 the capillaries, which are going to form the capillary plexuses of the 

 mucous membrane* These tubes open upon the floors of the gastric 

 cells of the stomach ; their number is variable, but they average 

 from five to nine tubes in each cell. 



910. A delicate distribution of capillaries with wide meshes runs 

 around the tubes, and these are the vessels seen in those cells, pre- 

 senting the most open surface, by which stomach may be discrimi- 

 nated from large intestine. 



911. There is much obscurity surrounding the origin of the gas- 

 tric juice; some authors supposing that it is secreted by the vessels 

 of the mucous membrane of the stomach, but we now know that the 

 stomach, in its submucous tissue, is literally filled with glands, hence 

 called gastric glands ; these all secrete a fluid, and while some of 

 them are known to secrete the true gastric juice, the function of the 

 remainder remains to be discovered. 



912. These glands are not so well developed nor so conspicuous 

 in man, as in other animals, and two views of them are selected, one 

 from the Dog, and the other from the Calf. 



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