Organic Non-electrolytes 1 87 



similarly found that in the dog parotid stimulated by pilocarpine 

 the glucose threshold averaged 500 mg/100 ml. Hebb and Stavraky 

 also made the interesting observation that administration of enough 

 adrenaline to cause a flow of saliva resulted in the appearance of 

 large amounts of glucose in the saliva, and that this increased 

 glucose permeability persisted for many hours after the initial 

 adrenaline injection. Sympathetic stimulation was not effective in 

 producing this response, but the adrenaline effect was not purely 

 pharmacological as was shown in experiments in which cats were 

 exposed to cold and were found to have glucose in their saliva due 

 to endogenous adrenaline release. Noradrenaline is less effective 

 (Martin, 1959) in producing this response and perhaps the ineffec- 

 tiveness of sympathetic stimulation may be due to release only of 

 noradrenaline by the nerve terminals. This effect of adrenaline 

 is not peculiar to the submaxillary gland of the cat but is also 

 found in the dog submaxillary and blood glands and affects the 

 concentrations of amino-acids, creatinine, sucrose, electrolytes and 

 probably other constituents of saliva as well as glucose (Martin, 

 1959; Langstroth, McRae and Stavraky, 19386). It has recently 

 been found (Langley, Gunthorpe and Beall, 1958) that the sali- 

 vary glucose threshold is considerably lowered in dogs made dia- 

 betic with alloxan and is raised by insulin administration. Pearce 

 (191 6) claimed that phloridzin caused glucose to appear in saliva 

 in a proportion of dogs to which it had been given in doses large 

 enough to produce glycosuria. 



The relationship of saliva glucose to carbohydrate metabolism 

 both within the gland and in the body as a whole is a problem of 

 considerable interest. Johns (1933) has reviewed the fascinating 

 but conflicting clinical evidence showing a relationship between 

 pathological changes in the parotid gland and alterations in sys- 

 temic glucose metabolism. 



ASCORBIC ACID 



Ascorbic acid appears to be present in saliva although concen- 

 trations are smaller than in the plasma (Stuteville, 1935; Freeman 

 and Hafkesbring, 1951). 



ORGANIC NON-ELECTROLYTES 



Systematic studies of the permeability of the salivary glands to 

 organic non-electrolytes have been carried out by Amberson and 



