THE ACID OF THE GASTRIC JUICE. 359 



lactic acid or other organic acid is formed, which disproves the theory 

 that lactic acid is first formed and then decomposes sodium chloride, so 

 forming free hydrochloric acid. 1 



It may here be pointed out that experiments have been made by 

 Nencki and Schoumova-Simanowsky 2 to ascertain the possibility of 

 replacing the chlorine by other halogens, so as to form hydrobromic or 

 hydriodic acids. These experiments were performed on dogs operated 

 on by Pawlow's method, 3 and the animals were fed with food in which 

 sodium chloride was as far as possible absent. Some had added to their 

 food sodium bromide, others sodium iodide. The administration of 

 sodium bromide resulted in the animals becoming so ill after a w T eek or 

 so that the experiments had to cease. The gastric juice was secreted as 

 before, but the hydrochloric acid was largely replaced by hydrobromic 

 acid. In the case of those dogs to which sodium iodide was administered, 

 though less general disturbance resulted from the administration than 

 was the case with sodium bromide, yet the amount of hydriodic acid 

 replacing hydrochloric acid was very small. 



Reciprocity between the secretion of hydrochloric acid and the reaction 

 of the urine. That the hydrochloric acid of the gastric juice is formed 

 from the chlorides of the blood plasma, is likewise shown by Maly's 4 

 observation that at the same period after a meal at which the secretion 

 of gastric juice is at a maximum, the acidity of the urine is at a minimum, 

 and may be replaced by an alkaline reaction. One function of the kidneys 

 is to preserve unaltered in degree the alkalinity of the blood. If now 

 neutral salts, such as sodium chloride, be removed from the blood, split 

 up in some manner by the agency of the gastric gland cell into hydro- 

 chloric acid and sodic hydrate, of which the hydrochloric acid is sent 

 towards the stomach cavity, while the alkali is expedited in the opposite 

 direction back to the blood stream, it follows that the alkalinity of the 

 blood will be increased. Hence, to preserve equilibrium, the kidneys 

 must excrete a less proportion of acid salts, or, if the rate of increasing 

 alkalinity of the blood demands it, must separate an alkaline fluid from 

 the blood. This is experimentally found to be the case. Under ordinary 

 circumstances, the kidneys preserve the constant value of the alkalinity 

 of the blood, by excreting phosphates of the alkalies so proportioned that 

 the reaction is acid, but during active digestion, 2 to 4 hours after a full 

 meal such as dinner, the relative amounts of bases and phosphoric acid 

 are so altered that the reaction becomes neutral or faintly alkaline, or, as 

 it is often commonly but not very exactly expressed, in the first case 

 monosodic phosphate (NaH 2 P0 4 ) is secreted with acid reaction ; in the 

 second, disodic phosphate Na 2 HP0 4 with alkaline reaction. 5 



Theories as to the mode of origin of the hydrochloric acid. Many 

 ingenious theories have been proposed to account for the specific function 

 of the gland cells of the stomach, of splitting up such a stable substance 



1 See p. 352. 



2 Arch. f. exper. Path. u. PhartnakoL, Leipzig, 1894, Bd. xxxiv. S. 313. 



3 See article on " Mechanism of Gastric Secretion." 



4 Ann. d. Chem., Leipzig, 1874, Bd. clxxiii. S. 232. See also Quincke, JaJircsb. ii. d. 

 Fortschr. d. Thier-Chcm., Wiesbaden, 1874, Bd. iv. S. 241 ; Stein, ibid., 1876, Bd. vi. 

 S. 161. 



5 The reaction will really vary according to the relative amounts of base and acid 

 present. Monosodic phosphate alone dissolved in water has an acid reaction, disodic 

 phosphate similarly has an alkaline reaction, and mixtures in varying proportions can 

 have acid, neutral, or alkaline reaction. In a complex mixture such as urine, no one can 

 say to what the reaction is due, but only that there is an excess of alkali or acid. 



