DIGESTION 241 



too great (hypersecretion) ; (2) the total amount of 

 juice may be normal, but the percentage of HC1 which 

 it contains too high (hyperchlorhydria) ; (3) there may 

 be errors in the time-rate of the secretion e.g., it 

 may be poured out too fast if the glands are irritable or 

 overexcited, or it may be produced too slowly. 



The experiments of Pawlow appear to show that in 

 the dog, at least, there is a certain adaptation of the 

 composition and strength of the gastric juice to the kind 

 of food which has to be digested. For example, for 

 bread-protein five times more pepsin is poured out than 

 for protein in milk, and for flesh-protein 25 per cent, 

 more than on that of milk. It is doubtful, however, 

 whether such variations occur in man,* although pos- 

 sibly if one particular kind of food is taken for a 

 long time such an adaptation may be arrived at, and a 

 * digestive habit ' for that form of diet established. 



Motility. 



1. Tonicity. In the empty stomach there is normally 

 a slight degree of tension present which keeps up a 

 pressure within it, which has been estimated in man as 

 equal to a manometric pressure of about 4 to 5 centi- 

 metres of water.f This is due in part to a slight tonic 

 contraction of the muscular coat, and in part also, 

 perhaps, to the contractile pressure exerted by the 



* See Penzoldt, Deuts. Archiv f. Kim. Med., 1894, liii. 209, 

 and Schiile, Zeit. f. Klin. Med., 1895, xxviii. 461, and 1896, 

 xxix. 49. 



t See Dobrovici, Archiv f. Verdcwungskrankh., 1907, xiii. 78 ; 

 also Moritz, Zeit. /. Biologie, 1895, xxxii. 313. 



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