SALIVA. 5 



The inorganic constituents in 1000 parts of saliva are, accord- 

 ing to Mitscherlich, chloride of calcium, 1-8; lactate of potash, 

 95 ; lactate of soda, -24 ; soda, probably combined with mucus, 

 1*64; phosphate of lime, '17; silica, "15. 



[According to Dr. Wright, pure saliva is a limpid fluid, having 

 a faint blue tinge, and a slight degree of viscidity. It is per- 

 fectly uniform in consistence, and unobscured by frothiness or 

 flocculi. It possesses a faint sickly odour sui generis, due to 

 its constituent, ptyalin : this odour is strengthened by heat and 

 by most acids, but alkalies diminish and destroy it. 



The saliva even of healthy people varies considerably in its 

 specific gravity. It is always denser after a meal than during 

 fasting ; and generally denser in an evening than in a morning. 

 But the converse is usually the rule with dyspeptics. Dr. Wright 

 found that animal (especially fatty) diet, and alcoholic stimulants, 

 have a tendency to thicken the saliva ; oysters, and vegetable 

 diet, he says, produce an opposite effect. He states, as the 

 result of many trials and observations, that healthy saliva is 

 mostly of a sp. gr. of 1007-9. When above 1010-0 or below 

 1003-0, the secretion maybe considered to be morbid. Healthy 

 saliva, he affirms, is either alkaline or neutral, generally the 

 former. If saliva be heated, it not uncommonly acquires an 

 acidity in a few minutes, but this chiefly happens to neutral saliva. 



Dr. Wright believes in the existence of the principle called 

 ptyalin, though he separates it from saliva by a new process. 

 This process is " to pass saliva through ordinary filtering paper, 

 and, after filtration shall have been completed, to exhaust the 

 residue with sulphuric ether; the ethereal solution contains 

 a fatty acid and ptyalin. 1 It is to be allowed to evaporate 

 spontaneously, and the residue left by evaporation is to be placed 

 upon a filter and acted upon by distilled water, which dissolves 

 the ptyalin and leaves the fatty acid. If the aqueous solution 

 be carefully evaporated to dryness, the " salivary matter will be 

 obtained in a pure state/' " Ptyalin," he says, " as thus pre- 

 pared, is a yellowish-white, adhesive, and nearly solid matter, 

 neither acid nor alkaline, readily soluble in ether, alcohol, and 



1 A reference to vol. i, p. 24, will show that Wright's ptyalin differs in several 

 respects from the ptyalin described by Simon. In truth, little is known regarding 

 this constituent. 



