GASTRIC JUICE, AND STOMACH DIGESTION. 147 



The comparative digestibility of different substances varies more 

 or less in different individuals according to temperament ; but the 

 above list undoubtedly gives a correct average estimate of the time 

 required for stomach digestion under ordinary conditions. 



A very interesting question is that which relates to the total 

 quantity of gastric juice secreted daily. Whenever direct experi- 

 ments have been performed with a view of ascertaining this point, 

 their results have given a considerably larger quantity than was 

 anticipated. Bidder and Schmidt found that, in a dog weighing 

 34 pounds, they were able to obtain by separate experiments, con- 

 suming in all 12 hours, one pound and three-quarters of gastric 

 juice. The total quantity, therefore, for 24 hours, in the same ani- 

 mal, would be 3J pounds; and, by applying the same calculation to 

 a man of medium size, the authors estimate the total daily quantity 

 in the human subject as but little less than 14 pounds (av.). This 

 estimate is probably not an exaggerated one. In order to deter- 

 mine the question, however, if possible, in a different way, we 

 adopted the following plan of experiment with the gastric juice of 

 the dog. It was first ascertained, by direct experiment, that the 

 fresh lean meat of the bullock's heart loses, by complete desiccation, 

 78 per cent, of its weight. 300 grains of such meat, cut into small 

 pieces, were then digested for ten hours, in |iss of gastric juice at 

 100 F.; the mixture being thoroughly agitated as often as every 

 hour, in order to insure the digestion of as large a quantity of meat 

 as possible. The meat remaining undissolved was then collected 

 on a previously weighed filter, and evaporated to dryness. The 

 dry residue weighed 55 grains. This represented, allowing for the 

 loss by evaporation, 250 grains of the meat, in its natural moist 

 condition ; 50 grains of meat were then dissolved by 3iss of gastric 

 juice, or 33J grains per ounce. 



From these data we can form some idea of the large quantity of 

 gastric juice secreted in the dog during the process of digestion. 

 One pound of meat is only a moderate meal for a medium-sized 

 animal ; and yet, to dissolve this quantity, no less than thirteen pints 

 of gastric juice will be necessary. This quantity, or any approxi- 

 mation to it, would be altogether incredible if we did not recollect 

 that the gastric juice, as soon as it has dissolved its quota of food, 

 is immediately reabsorbed, and again enters the circulation, together 

 with the alimentary substances which it holds in solution. The 

 secretion and reabsorption of the gastric juice then go on simulta- 

 neously; and the fluids which the blood loses by one process are 



