264 PHYSIOLOGICAL ACTIONS OF THE SALIVA. 



(6) Desquamated squamous epithelium is never absent, and is present in 

 abundance in association with catarrh of the buccal cavity (Fig. 92, 8). 



(c) Living organisms, which grow as saprophytes upon the buccal fluid and 

 remains of food, at times in carious teeth, consist of the threads of the leptothrix 

 buccalis (Fig. 92, 12), which turn blue, as a rule, on addition of iodin, and multiply 

 with enormous rapidity. Leptothrix vegetations enter the dental tubules and 

 cause caries of the teeth. The zooglea-form of the leptothrix appears as a cream- 

 like, yellowish, smeary deposit on the teeth. Miller found in all healthy human 

 beings, in addition to the ordinary leptothrix buccalis, another variety, the lepto- 

 thrix buccalis maxima, also the iodococcus vaginatus, the bacillus buccalis maximus, 

 the spirillum sputigenum and the spirochaeta dentium. Further, pathogenic 

 bacteria may be present, as, for instance, those of pneumonia, of diphtheria, etc. 



Chemical Properties. (a) Organic constituents : a globulin-like albu- 

 minous substance, mucin, ptyalin; fats and urea are present only in 

 traces; about 130 mg. of potassium or sodium sulphocyanid in twenty- 

 four hours. 



(b) Inorganic constituents: sodium chlorid, potassium chlorid, potas- 

 sium sulphate, alkaline and earthy phosphates and ferric phosphate. 



According to Schonbein, saliva contains traces of nitrous salts, which are recog- 

 nizable from the yellow color produced by metadiamidobenzol in saliva diluted five 

 times with water after addition of a few drops of dilute sulphuric acid ; also traces 

 of ammonia. Fresh saliva is said to contain hydrogen dioxid, which oxidizes 

 the ammonia to nitrous acid; though when the reaction of the saliva is acid 

 nitric acid is formed. 



Abnormal Constituents of the Saliva.. In cases of diabetes lactic acid has been 

 found as a result of decomposition of the sugar. It dissolves the calcium of the 

 teeth and may thus give rise to caries, as in cases of diabetes, v. Frerichs found 

 leucin, and an increased amount of urea and albumin were observed in cases of 

 nephritis, and uric acid in cases of uremia. Of foreign substances that are admin- 

 istered there appear in the saliva mercury, potassium, metallic and free iodin and 

 bromin, the last displacing an equivalent amount of chlorin from the salivary 

 chlorids, lead, morphin, lithium, and sodium chlorid. 



Of the salivary glands in the new-born infant only the parotid contains ptyalin. 

 In the submaxillary gland and in the pancreas the diastatic ferment appears to 

 be formed not earlier than the end of the second month. Therefore the nourish- 

 ment of infants with starches is not advisable. It is a remarkable fact that in 

 new-born infants suffering from thrush (due to oidium albicans) no ptyalin is 

 demonstrable in the saliva. For the infant that takes milk alone, the diastatic 

 action of the saliva is not indispensably necessary. Therefore, the mucous mem- 

 brane of the mouth appears to be but slightly moistened during the first two 

 months, though an abundance of saliva is secreted later . Also, the glands usually 

 attain a considerable size only after the first half-year of life. The irruption of 

 the first teeth causes the secretion of much saliva in consequence of the irritation 

 of the buccal mucous membrane. 



PHYSIOLOGICAL ACTIONS OF THE SALIVA. 



The most important action of the saliva is amylolytic or diastatic, 

 that is, the conversion of starch into sugar and dextrin. This is due 

 to the ptyalin, an unformed, hydrolytic ferment or enzyme which, even 

 when present in small amounts, causes the starch to take up water and 

 become soluble, with absorption of heat, although the ferment itself 

 undergoes no material change. Ptyalin is not present in the saliva of 

 true carnivora. 



According to Dubrunfaut, O' Sullivan, Musculus and v. Mering, maltose and 

 dextrin, both soluble in water, are formed from starch (or glycogen) by the dias- 

 tatic ferment of the saliva (and of the pancreas) : 



