148 DIGESTION. 



rious, not only for dry food, like bread, but even for that of a tolerably 

 moist consistency, like fresh meat. The animals also became very 

 thirsty, and were constantly ready to drink." 



Bernard 1 also found that the only marked effect of cutting off the flow 

 of saliva from the mouth was a difficulty in the mechanical processes of 

 mastication and deglutition. He first administered to a horse 500 

 grammes of oats, in order to ascertain the rapidity with which mastica- 

 tion would naturally be accomplished. The above quantity of grain was 

 thoroughly masticated and swallowed at the end of nine minutes. An 

 opening had been previously made in the esophagus at the lower part 

 of the neck, so that none of the food reached the stomach ; but each 

 mouthful, as it passed down the oesophagus, was received at the cesopha- 

 geal opening and examined by the experimenter. The parotid duct on 

 each side of the face was then divided, and another similar quantity of 

 oats given to the animal. Mastication and deglutition were both found 

 to be immediately retarded. The alimentary masses passed down the 

 03sophagus at longer intervals, and their interior was no longer moist 

 and pasty, as before, but dry and brittle. Finally, at the end of twenty- 

 five minutes, the animal had succeeded in masticating and swallowing 

 only about three-quarters of the quantity which he had previously dis- 

 posed of in nine minutes. 



It appears from the experiments of Magendie, Bernard, and Las- 

 saigne, on horses and cows, that the quantity of saliva absorbed by 

 the food during mastication is in direct proportion to its hardness and 

 dryness, but has no particular relation to its chemical qualities. These 

 experiments were performed as follows : The oesophagus was opened at 

 the lower part of the neck, and a ligature placed upon it, between the 

 wound and the stomach. The animal was then supplied with a pre- 

 viously weighed quantity of food, and this, as it passed out by the oeso- 

 phageal opening, was received into appropriate vessels and again 

 weighed. The difference in weight, before and after swallowing, indi- 

 cated the quantity of saliva absorbed by the food. The following table 

 gives the results of some of Lassaigne's experiments, performed upon a 

 horse. 



Kind of Food employed. Quantity of Saliva absorbed. 



For 100 parts of hay 400 parts. 



barley meal 186 " 



oats 113 " 



green stalks and leaves . . 49 " 



It is evident from the above facts, that the quantity of saliva pro- 

 duced has not so much to do with the chemical character of the food 

 as with its physical condition. When the food is dry and hard, and 

 requires much mastication, the saliva is secreted in abundance; when it 

 is soft and moist, a smaller quantity of the secretion is poured out ; and 

 finally, when the food is taken in a fluid form, as soup or milk, or 

 reduced to powder and moistened artificially with a large quantity of 



1 Leqons de Physiologic Experimental. Paris, 1856, p. 146. 



