128 DIGESTION. 



duct in the human subject ; from which it was supposed that the 

 total amount secreted by all the glands was from ten to twelve 

 ounces daily. As this man was a hospital patient, however, and 

 suffering from constitutional debility, the above calculation cannot 

 be regarded as an accurate one, and accordingly Bidder and Schmidt 1 

 make a higher estimate. One of these observers, in experimenting 

 upon himself, collected from the mouth in one hour, without using 

 any artificial stimulus to the secretion, 1500 grains of saliva; and 

 calculates, therefore, the amount secreted daily, making an allow- 

 S ance of seven hours for sleep, as not far from 25,000 grains, or 

 about three and a half pounds avoirdupois. 



On repeating this experiment, however, we have not been able to 

 collect from the mouth, without artificial stimulus, more than 556 

 grains of saliva per hour. This quantity, however, may be greatly 

 increased by the introduction into the mouth of any smooth un- 

 irritating substance, as glass beads or the like; and during the 

 mastication of food, the saliva is poured out in very much greater 

 abundance. The very sight and odor of nutritious food, when the 

 appetite is excited, will stimulate to a remarkable degree the flow 

 of saliva ; and, as it is often expressed, " bring the water into the 

 mouth." Any estimate, therefore, of the total quantity of saliva, 

 based on the amount secreted in the intervals of mastication, would 

 be a very imperfect one. We may make a tolerably accurate 

 calculation, however, by ascertaining how much is really secreted 

 during a meal, over and above that which is produced at other times. 

 We have found, for example, by experiments performed for this 

 purpose, that wheaten bread gains during complete mastication 55 

 per cent, of its weight of saliva ; and that fresh cooked meat gains, 

 under the same circumstances, 48 per cent, of its weight. We have 

 already seen that the daily allowance of these two substances, for a 

 man in full health, is 19 ounces of bread, and 16 ounces of meat. 

 The quantity of saliva, then, required for the mastication of these 

 two substances, is, for the bread 4,572 grains, and for the meat 3,360 

 grains. If we now calculate the quantity secreted between meals 

 as continuing for 22 hours at 556 grains per hour, we have : 



Saliva required for mastication of bread = 4572 grains. 

 " " " " meat = 3360 " 



secreted in intervals of meals = 1 2232 " 



Total quantity in twenty-four hours = 20164 grains ; 



or rather less than 3 pounds avoirdupois. 



1 Op. cit., p. 14. 



