SALIVA. 7 



cases, it is much more abundant." He says that saliva, in its 

 healthy state, contains also oxygen gas, which it can be made 

 to evolve on the application of heat. This in some measure 

 aids its digestive powers ; for he found that saliva which had 

 been exposed for some hours to an atmosphere of oxygen, con- 

 verted a much greater quantity of starch into gum and sugar 

 than other saliva which had not been so exposed. This state- 

 ment, founded upon a great number of comparative experiments 

 was made by Dr. Wright long before the apparently less correct 

 observation of Liebig, that the saliva collects " bubbles of air" 

 to assist the digestive function. In pure saliva there are no 

 " bubbles of air ;" the absorbed gases are carbonic acid and 

 oxygen, the latter only contributing to the digestive properties 

 of the fluid. As the result of numerous analyses, the process 

 of which Dr. Wright has fully detailed, he gives the following 

 as the constituents of the healthy secretion : l 



Water .... 988-1 



Ptyalin . . . 1'8 



Fatty acid ... '5 



Chlorides of sodium and potassium . 1-4 



Albumen with soda . . '9 



Phosphate of lime . . *6 



Albuminate of soda . . "8 



Lactates of potash and soda . *7 



Sulphocyanide of potassium . '9 



Soda ... -5 



Mucus, with ptyalin . . 2-6 



I/Heretier has recorded the mean of ten analyses of the 

 saliva of healthy persons, collected while fasting : 



Water . . . 986-5 



Organic matter . . 12-6 



Inorganic matter . . -9 



The salivary matter, or ptyalin, formed 2'5 of the 12'6 parts 

 of organic matters. 



In children, the amount of water is generally increased. As 

 a mean of four analyses, he found : 



1 Der Speichel in physiologischer, diagnostischer, und therapeutischer Beziehung, 

 p. 28, Wien, 1844. Dr. Wright's investigations first appeared in the Lancet. 



