CHAP. I.] EXCRETION OF FOREIGN SUBSTANCES IN SALIVA. 51 



commences to decline, not being entirely destroyed till the tempera- 

 ture approaches 80 C. 



It has been shewn, however, by O'Sullivan and by Brown and 

 Heron that the changes which are brought about by malt-diastase 

 are influenced in a very marked manner by temperature. 



The range of temperature at which the salivary ferment acts 

 most powerfully is according to Roberts very wide, viz. from 30 45. 

 According to Kjeldahl the most favourable temperature is 46 C. 2 

 The ferment is however destroyed when its solutions are heated to 

 between 65 and 70 (Roberts), i.e. at a temperature 10 degrees 

 lower than that which destroys the action of malt. 



2. Salicylic acid when present in the proportion of 0'05 per cent, 

 at once stops all action of malt-diastase upon starch-paste. In such 

 proportions, it exerts no perceptible action on the salivary ferment. It 

 is only when present in the proportion of O'l per cent, that the least 

 slowing influence is perceptible, and as much as 1 per cent, must be 

 present in order to arrest entirely the action of the ferment. 



SECT. 4. EXCRETION OF MEDICINAL SUBSTANCES IN THE SALIVA. 



Certain medicinal agents, as potassium iodide, are excreted in the 

 saliva. Others are not, e.g. potassium ferrocyanide. Mercury, of 

 which medicinal preparations induce, under certain circumstances, 

 profuse salivation, has been detected in saliva. 



It is said that lead can be detected 3 in the saliva of persons 

 suffering from lead-poisoning, in whom salivation has been induced 

 by injection of pilocarpin. Under similar circumstances arsenic has 

 not been detected. 



Rapidity of Langley and Fletcher found (1) on injecting 50 c.c. 

 secretion of of a solution of lithium nitrate into the blood that the 

 certain salts first drop of saliva secreted both from the subrnaxillary 

 when injected an( j f rom ^he p aro tid gland shewed the lithium band in 

 ood ' the spectroscope; (2) on injecting 50 c.c. of a solution of 

 potassium iodide into the blood, the salt was preseni in all the drops 

 of saliva after the first six, appearing first in 1J|je subrnaxillary 

 secretion, which flows more rapidly than the parotid, although the 

 quantity of iodide was larger in the parotid than in the submaxillary 

 saliva. 



1 Kiihne, Lehrbuch, p. 21. 



- Kjeldahl, ' Untersuchungen iiber zuckerbildende Fermente.' Abstracted from the 

 original Swedish by Hammarsten, Maly's Jahresbericht, Vol. ix. p. 381. 



3 Pouchet, 'Kecherche des substances medicamenteuses et toxiques dans la Salive.' 

 Comptes Rendus, Vol. LXXXIX. p. 244. 



4 Langley and Fletcher, Op. cit. pp. 149 and 150. 



42 



