64 J0RN Hess Thaysen 



In parotid saliva, however, a definite rise in potassium 

 concentration is noted at rates smaller than 15 mg. per gram 

 gland per minute. This finding is in agreement with the results 

 of Langstroth, McRae and Stavraky (1938) and Burgen (1956). 

 A similar rise in potassium concentration possibly occurs at 

 low rates of sweat secretion (Kuno, 1956), but could not be 

 demonstrated with the experimental technique employed by 

 Schwartz and Thaysen (1956). In the two other secretions a 

 rise in potassium concentration at low secretory rates has 

 never been observed. 



The Excretion of Anions: 



The main anion of sweat and tears is chloride. This anion 

 accounts for about 80 per cent of the sum of the concentrations 

 of sodium and potassium in the tear fluid. Chloride concentra- 

 tion of sweat is not depicted in Fig. 1, but Locke and his co- 

 workers (1951) found the following relation: sodium= 

 1-12 chloride-j-3 m-equiv./l. 



The chief anion of parotid saliva and pancreatic juice is 

 bicarbonate. With increasing secretory rate the concentra- 

 tion of bicarbonate rises in both secretions and reaches a 

 maximum of about 60 m-equiv./l. in parotid saliva and about 

 90-130 m-equiv./l. in pancreatic juice. When this maximum 

 concentration (which is subject to individual variation) has 

 been arrived at, the concentration of bicarbonate remains 

 independent of further increases in the rate of secretion. The 

 concentration of chloride varies inversely with that of bi- 

 carbonate. In both secretions and at all rates the sums of the 

 concentrations of the two anions equal about 80-90 per cent 

 of the sums of the concentrations of sodium and potassium. 



The following hypothesis has been put forward to explain 

 the demonstrated differences in the excretion of the main 

 cations. In all four glands a precursor solution is formed in 

 which the concentration of sodium is independent of the rate 

 of precursor formation. In the sweat and parotid glands, but 

 not in the other two glands, sodium is consequently reab- 

 sorbed by a process of a limited maximal capacity (Thaysen, 



