222 PRACTICAL PHYSIOLOGY 



stomach, and another of the pyloric end, by Pawlow's method, it 

 will be found that the secretion of the former alone contains the free 

 acid. If now the mucous membrane from these two, regions of the 

 stomach be examined microscopically it will be found that the glands 

 of the cardiac portion contain besides the ordinary secreting cells, 

 which are similar to those of the pyloric portion large round cells. To 

 these cells, then, probably belongs this acid secreting power, i.e. they 

 can take up the acid and transfer it to the lumen of the gland. 1 



If an animal be fed on bromides instead of chlorides, hydrobromic 

 takes the place of hydrochloric acid. 



The Uses of the Free Acid are Two: (1) It is necessary for the efficient 

 action of pepsin, and (2) it acts as an antiseptic, preventing fermenta- 

 tion in the stomach, which would otherwise certainly occur, since a 

 considerable number of micro-organisms are present in our food-stuffs, 

 and nothing could be more favourable for their growth than the semi- 

 fluid contents of half-digested food kept at body temperature. A 

 certain form of dyspepsia is due to deficiency of hydrochloric acid in 

 the gastric secretion. If the reaction of the gastric contents in such a 

 case be tested, however, it is found to be strongly acid, and if the 

 amount of this acidity be determined (see Advanced Course, p. 445) it 

 may be found to be greater than that of healthy gastric juice. By 

 applying appropriate tests the cause of the acidity is found to be chiefly 

 due to lactic acid. This is developed by the growth of certain micro- 

 organisms (bacillus lactis) on carbohydrates (see Milk, p. 188). This 

 lactic acid may be further decomposed, giving rise to butyric acid. 



(1) C 12 H 32 U + H 2 = 4C ? H 6 3 



Lactose. Lactic acid. 



(2) 4C 3 H 6 3 = 2C 4 H 8 2 + 4C0 2 + 4H 2 



Lactic acid. Butyric acid. 



By examining the equations it will be noticed that gas (C0 2 ) is 

 evolved during the transformation of lactic into butyric acid. The 

 accumulation of this in the stomach leads to 'flatulence.' 



The presence of lactic acid in these cases can be detected by employ- 

 ing Uffelmann's reaction (see Milk, p. 188). 



The Organic Matter. If pure gastric juice, obtained by Pawlow's 

 method, be cooled to C. a precipitate falls down. On analysis this is 

 found to have nearly the same percentage composition as proteid, and on 

 testing its action on a solution of proteid it is found to be 'pepsin.' 



1 As to the exact rdle which these * oxyntic ' cells play in this mechanism there 

 is considerable difference of opinion. Some state that the above-mentioned 

 chemical reaction takes place in their bodies, others that they simply transfer 

 4 H ' ions, which then react with the chlorides in the stomach itself. 



