416 



SALIVA. 



globules are remarkably transparent, 

 smaller than the more opake. 



Specific gravity. The specific gravity of 

 healthy saliva is about 1007*9, according to 

 the experiments of Dr. Wright. It is denser 

 after food has been taken. Mitscherlich gives 

 the specific gravity of saliva at 1006*1 to 

 1008-8, which agrees with Dr. Wright's ob- 

 servations. 



Some discrepancy of opinion exists as 

 to the reaction of saliva in respect to alka- 

 linity or acidity. Tiedemann and Gmelin, 

 and also Schultze, state fresh saliva to be 

 alkaline. The latter chemist, has, indeed, 

 attempted to define its saturating power. He 

 also considers that it may become acid if 

 retained long in the mouth, and that its alka- 

 linity when fresh is dependent on ammonia. 

 This is denied by Mitscherlich, who says that 

 no ammonia is given off when fresh saliva is 

 heated, and that the alkalinity depends on the 

 presence of a fixed alkali. 



I have myself found that saliva, so far 

 from losing its alkalinity by evaporation, has 

 this quality increased, and am inclined to re- 

 gard the reaction as dependent on the pre- 

 sence of tribasic phosphate of soda (a salt re- 

 acting on test paper as an alkali), as has been 

 stated by Enderlin. 



Chemistry. Berzelius estimates the so! ills of 

 saliva at about 1 per cent. From the solid re- 

 sidue he extracted osmazome, an alkaline lac- 

 tate, and chlorides of potassium and sodium by 

 digestion with alcohol. That portion which 

 the alcohol left undissolved consisted of soda, 

 mucus, and a peculiar animal matter, which has 

 been called " salivary matter," or " ptyalin." 

 The mucus can be separated from this salivary 

 matter and soda by digestion in cold water, 

 which dissolves the two latter. The mucus 

 thus separated by Berzelius yielded on in- 

 cineration a large proportion of phosphate of 

 lime. 



The following is his analysis of saliva : 



Water 992*9 



Ptyalin 2*9 



Mucus - - - - - 14 

 Animal extractive matter and al- 

 kaline lactates - -9 

 Chloride of sodium - - 1*7 

 Soda - -2 



lOOO'O 



Tiedemann and Gmelin obtained from 1*14 

 to T19 percent, of solid residue by evapo- 

 rating saliva. From this, 0*25 parts of ash 

 were obtained, of which 0-203 were composed 

 of salts soluble in water, the remainder con- 

 sisting of earthy phosphates. 



The following is a list of the constituents 

 of the saliva, according to the above-men- 

 tioned chemists : 



1. Water. 



2. A substance soluble in alcohol, and in- 

 soluble in water (fat containing phosphorus). 



3. Matters soluble both in alcohol and 

 water (osmazome, chloride of potassium, lac- 



and tate of potash, and sulpho-cyanuret of potas- 

 sium. 



4. Animal matter soluble in boiling alcohol, 

 but precipitated during cooling, with sulphate 

 of potash and some chloride of potassium. 



5. Matters soluble in water only (salivary 

 matter with abundant phosphate, and some sul- 

 phate of an alkali, and chloride of potassium). 



6. Matters soluble neither in water nor in 

 alcohol (mucus, probably some albumen, with 

 alkaline carbonate, and phosphate). 



Mitscherlich gives the following analysis of 

 the saline ingredients of saliva : 



Chloride of potassium - percent. 0*18 

 Potash (in combination with 1 A _ 

 lactic acid) - j 



Soda 0-024 



Lactic acid 



Soda (combined with mucus) - 0*164 



Phosphate of lime ... 0'017 



Silica 0-015 



Simon made an analysis of his own saliva, 

 and gives the following as the result : 



Fat containing cholesterine - 0'525 

 Ptyalin with extractive matter - 4*375 

 Extractive matter and salts - 2*450 

 Albumen, mucus, and cells - 1*400 

 Water 991*225 



Simon* adopted the following process in 

 order to complete the above analysis. A 

 known weight of saliva was first evaporated 

 to dryness ; the loss of weight thus indicated 

 the proportion of water. The residue was 

 treated with ether, which extracted the fats. 

 The solid mass remaining was next treated 

 with water, which dissolved out the ptyalin, 

 extractive matters, and salts, leaving behind 

 mucus, albumen, and cells. 



Dr. Wright has experimented on saliva most 

 industriously, and has entered at some length 

 on the peculiarities of ptyalin, but evidently 

 speaks of a very different constituent to that 

 described by Berzelius and Simon. Accord- 

 ing to the mode of analysis adopted by these 

 two latter chemists, the ptyalin of Wright will 

 be estimated with the fatty constituents, 

 among which it most probably holds its proper 

 place. 



His process of extraction is as follows : " 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. It is to be allowed to evaporate 

 spontaneously, and the residue left by evapo- 

 ration is to be placed upon a filter and acted 

 upon by distilled water, which dissolves the 

 ptyalin and leaves the fatty acid. If the aque- 

 ous solution be carefully evaporated to dry- 

 ness, the salivary matter will be obtained in a 

 pure state. Ptyalin, thus prepared, is a nearly 

 solid matter, adhesive, and of a yellowish co- 

 lour ; it is neither acid nor alkaline, readily 



* In framing this article, much valuable informa- 

 tion has been derived from Simon's work on Phy- 

 siological and Pathological Chemistry, translated 

 by Dr. Day for the Sydenham Society. 



