430 DIGESTION. 



POPIELSKI also disputes the assumption of PAWLOW that the secretion of 

 saliva (in dogs) accommodates itself to the kind of irritant and to the 

 kind of food ; although the theory that in man there is an accommodation 

 of the secretion to circumstances has found supporters, yet belief in it 

 is not general. 1 



The mixed buccal saliva in man is a colorless, faintly opalescent, 

 slightly ropy, easily frothing liquid without special odor or taste. It 

 is made turbid by epithelium cells, mucous and salivary corpuscles, 

 and often by food residues. Like the submaxillary and parotid saliva, 

 on exposure to the air it becomes covered with an incrustation consisting 

 of calcium carbonate and a small quantity of an organic substance, or 

 it gradually becomes cloudy. Its reaction is generally alkaline to litmus. 

 The degree of alkalinity varies considerably not only in different indivi- 

 duals but also in the same individual during different parts of the day, 

 so that it is difficult to state the average alkalinity. According to CHITTEN- 

 DEN and ELY it corresponds to the alkalinity of 0.8 p. m. Na 2 CO3 solu- 

 tion, or to 0.2 p. m. solution according to COHN. According to FOA the 

 the actual alkalinity (OH-ion concentration) is always considerably 

 less than that found by titration, and the reaction determined elestro- 

 metrically is very nearly neutral. The reaction may also be acid, as 

 found to be the case by STICKER some time after a meal, but this is not 

 true, at least for all individuals. The specific gravity varies between 

 1.002 and 1.008, and the quantity of solids between 5 and 10 p. m. Accord- 

 ing to CoHN, 2 J= 0.20 on an average, and the amount of NaCl is 1.6 

 p. m. The solids, irrespective of the form-constituents mentioned, 

 consist of protein, mucin, oxidases, 3 two enzymes, ptyalin and maltase, 

 and mineral bodies. It is also claimed that urea is a normal constituent 

 of the saliva. The mineral bodies are alkali chlorides, bicarbonates of 

 the alkalies and calcium, phosphates, and traces of sulphates, nitrites, 

 ammonia, and sulphocyanides, which latter average about 0.1 p. m. 

 (MuNK and others). Smaller quantities, 0.03-0.04 p. m., are found in 

 the saliva of non-smokers (SCHNEIDER and KRUGER), while from ordinary 

 smokers the quantity of sulphocyanides may rise to 0.2 p. m. (FLECK- 

 SEDER 4 ). 



1 See Zebrowski, Pfliiger's Arch., 110; Neilson and Lewis, Journ. of biol. Chem., 4, 

 and with Scheele, ibid., 5. 



2 Chittenden and Ely, Amer. Chem. Journ., 4, 1883; Chittenden and Richards, 

 Amer. Journ. of Physiol., 1; Foa, Compt. rend. soc. biol., 58; Sticker, cited from 

 CentralbL f. Physiol., 3, 237; Cohn, Deutsch. med. Wochenschr., 1900. 



3 Bogdanow-Beresowski, cited from Biochem. CentralbL, 2, 653. 



4 Munk, Virchow's Arch., 69; Schneider, Amer. Journ. of Physiol., 5; Kriiger, 

 Zeitschr. f. Biologic, 37; Fleckseder, CentralbL f. innere Med., 1905. In regard to 

 the variation in the amount of various constituents in saliva see Fleckseder, 1. c., and 

 Tezner, Arch, internat. de Physiol., 2. 



