54 



Scientific Proceedings (36). 



secreted saliva. This is the case in the individuals (man) who re- 

 spond readily with varying secretion rates to stimuli of varying 

 strength (different strength of acids, or sand and acids). Thus the 

 slowly secreted saliva obtained on placing sand in the mouth con- 

 tains less pytalin than that secured on stimulation with acid. But 

 this direct relation between ptyalin concentration and secretion rate is 

 not a close one, hence a great difference in secretion rate is required 

 in order to demonstrate the difference in diastatic power. But this 

 is also true of the organic solids. We have not yet been able to 

 demonstrate this relation in the case of the rabbit's parotid saliva, 

 probably because of the rapid fatigue of the gland under experi- 

 mental conditions. 



3. Qualitatively different stimuli (acid, salt, sweet, bitter, 

 mechanical, agreeable, disagreeable) yield no constant difference in 

 the ptyalin concentration of the parotid saliva in man. But these 

 data are not conclusive owing to the practical impossibility of 

 keeping the secretion rate uniform. 



4. In varying directly with the organic solids and the secretion 

 rate it seems that the processes of ptyalin secretion differ from the 

 ferment-secreting processes in the other digestive glands. This 

 may be of significance in view of the fact that ptyalin seems to be 

 superfluous in digestion ; but, again, it is not plain whether this 

 condition signifies atrophy or incipient evolution. 



Pawlow's findings that in the dog dry sand in the mouth 

 causes a rapid secretion of a very dilute saliva seem not to apply 

 to man. In man the secretion rate varies directly with the strength 

 of the stimulus in the mouth and the saliva concentration depends 

 — within limits — on the secretion rate. There may be some dif- 

 ference in different mammalian groups as regards the efficacy of 

 the different reflex stimuli in the mouth, as acids in the mouth do 

 not produce a copious salivary flow from the rabbit's parotid. 



Unless the factor of secretion rate is controlled in all work on 

 saliva concentration and ptyalin concentration under different re- 

 flex stimuli and dietary conditions, the results obtained are not 

 conclusive. 



