256 The Physiological Role of Saliva 



demonstrated in many experimental animals (Grutzner, 1905; 

 Scheunert, 1906; Ellenberger, 1906) and in man (Prym, 1907; 

 Sick, 1907). 



In the fundus, therefore, acid gastric juice penetrates only slowly 

 into the bolus. A slight increase in acidity is actually assumed to 

 increase the activity of the salivary amylase and a rise in the con- 

 centration of chloride could do the same (Clifford, 1925 ; Ninomiya, 

 1940; Bernfeld, Staub and Fischer, 1948). The amylolytic action 

 of saliva has been shown to continue for 15 to 30 minutes in the 

 human stomach (Bergeim, 1926; Beazell, 1941). During this period 

 a considerable breakdown of polysaccharides occurs. In a series of 

 experiments on healthy men receiving a test meal Bergeim (1926) 

 found that on the average 76 per cent of the starch of mashed 

 potatoes and 59 per cent of the starch of bread had been converted 

 to maltose, an additional percentage being changed to dextrins. 

 Eventually the concentration of gastric juice becomes so high as 

 to inhibit the ptyalin. Strong acid and pepsin destroy the enzyme 

 (Gewiss, Rasp and Schwarz, 1926; Ninomiya, 1940). Salivary 

 amylase can therefore function in the intestine only provided that 

 it escapes the gastric juice, for instance in achylia. 



Numerous other enzymes, apart from ptyalin, have been found 

 in saliva ; in most instances mixed saliva has been used. Only a few 

 examples, and a very restricted number of references, may be 

 given. A lipolytic activity of saliva was observed by Scheer (1928), 

 Peluffo (1929), Katzenstein (1930) and many later investigators. 

 Esterase (Mahler and Chauncey, 1957), maltase (Hartles and Was- 

 dell, 1954), phosphatases (Giri, 1936; Glock, Murray and Pincus, 

 1938), hyaluronidase (Lisanti, 1950; Gibian, 1952), catalase and 

 peroxidase (Nickerson, Kraus and Perry, 1957; Wolfe and Turner, 

 1957), mucolytic enzymes (Knox, 1953), etc., have been detected in 

 saliva. It seems very unlikely that these enzymes contribute to the 

 digestive functions of saliva. In many cases the enzymes originate 

 from the oral bacterial flora (see, e.g., Chauncey, Lionetti, Winer 

 and Lisanti, 1954; Hartles and Wasdell, 1954). In other instances 

 they belong to the corpuscular elements of the saliva. This is well 

 illustrated by the early experiments in this field carried out by 

 Willstiitter, Bamann and Rohdewald (1929). These investigators 

 found that the amylolytic activity of saliva was not measurably 

 reduced when cells and bacteria were removed by centrifugation. 

 The tryptic activity of saliva, on the other hand, was diminished 



