QUANTITY OF SALIVA. 29 



maxillary, and sublingual saliva, the solid constituents amount 

 to very nearly the same, that is to say, to about 0*232 of a gramme, 

 of which 0*080 is organic and 0*152 inorganic matter. 



All determinations of the quantity of saliva secreted during a 

 more prolonged interval (as, for instance, 24 hours), must at most 

 be regarded as merely approximative, since the activity of the 

 salivary organs is dependent on very different influences and con- 

 ditions. The most common cause exciting a copious discharge of 

 saliva is the mastication of food ; it depends, however, very much 

 on the nature of the food, whether much or little saliva is effused 

 into the buccal cavity ; dry and hard food inducing a more copious 

 flow of saliva than food which is moist and soft ; indeed, the mere 

 motion of the lower jaw excites the act of secretion, and hence, 

 speaking or singing is always accompanied by the secretion of 

 saliva. That chemical irritants, such as are present in acid and 

 aromatic articles of food, and mechanical irritation, such as tick- 

 ling the palate, often produce an immediate secretion, is as well 

 known as that certain psychical influences always produce a similar 

 effect. It is especially important to observe that after the use of 

 food, the secretion continues for a long time ; a phenomenon which 

 appears not to be so referable to the irritation transmitted to the 

 salivary glands from the buccal cavity, as to the communication of 

 nervous action from the stomach during the process of digestion ; 

 for, on introducing food into the stomach, either through a gastric 

 fistula, or by means of an elastic tube in the oesophagus, we observe 

 that the secretion of gastric juice is accompanied by a copious 

 effusion of saliva. 



In order to determine the quantity of saliva required for different 

 kinds of food, experiments have been instituted by Mageiidie and 

 Rayer,* by Lassaigne,f and by Bernard, { on horses. The 

 oesophagus was exposed and opened, and the food which the 

 animals had swallowed was intercepted and removed. From these 

 experiments it followed, that straw and hay, as they pass down the 

 oesophagus, are mixed with four or five times their weight of 

 saliva, whilst seeds abounding in starch, as, for instance, oats, are 

 mixed with an equal quantity, or perhaps one and a half times as 

 much of saliva, and fresh green fodder with only half its weight ; 

 and that food mixed with water seems to take up scarcely any 

 saliva. Hence it appears as if, when food is taken, the secre- 



* Compt. rend. T. 21, p. 902. 



t Journ. de Chira. He'd. 1845, p. 472. 



t Arch. gen. de He'd. 4 S6r. T. 13, p. 22. 



