152 
MESSRS. J. N. LANGLEY AND H. M. FLETCHER 
the blood-flow tliroiigh the gland will lead to a diminished irritability of the gland, 
and, therefore, to a decrease in the rate of secretion of all the constituents of saliva. 
It will lead also directly to a considerable decrease in the secretion of water, to a less 
decrease in the secretion of salts, and to a still less decrease in the secretion of 
organic substance. With decreased blood-flow there will be less saliva, and this will 
contain a somewhat higher percentage of salts and a considerably higher percentage 
of organic substance. Further, with a given decrease of blood-flow, the stronger the 
stimulus, the higher will be the percentage of organic substance and of salts. 
Now, sympathetic saliva is just such saliva as, from the above-mentioned facts and 
deductions, we should expect to be produced by simultaneous stimulation of a secre¬ 
tory nerve and of glandular vaso-constricted flbres. Since the decrease in the blood- 
flow through the gland is much greater on stimulating the sympathetic than on bleed¬ 
ing, the sympathetic saliva should be secreted more slowly and contain a higher per¬ 
centage of organic substance than saliva secreted after bleeding. And this is the 
case. 
That the effect of decreasing the blood-flow through the gland is as we have given 
it, is supported by several other experiments besides the one we have quoted here; 
but we do not enter into the matter further, for two reasons—the one that there are 
certain of Heidenhain’s observations which appear to be contradictory to ours, and 
these we have not yet repeated, and the other that, since in the Cat stimulation 
of the sympathetic gives a saliva containing a low percentage of organic substance, it 
is desirable to investigate what in this case is the effect of a decreased blood flow. 
Summary or Chief Kesults. 
Heidenhain has shown that, when saliva is obtained by stimulating the chorda 
tympani, the percentage of salts in the saliva depends upon the rate of secretion; so 
that, the faster the secretion, the higher the percentage of salts is up to a limit of 
about ’6 per cent. Werther has come to the same conclusion, but finds that the 
percentage of salts may be as much as "77. 
In both Heidenhain’s and Werther’s experiments there are a considerable 
number of exceptions to this rule, attributed by them to variations in the rate of 
secretion of saliva during the time of collecting any one sample. 
We have repeated, with some modifications, the experiments of Heidenhain, paying 
especial attention to the rate of secretion of the saliva, and find, in 10 out of 11 cases, 
that his law of an increase in the percentage of salts with an increase in the rate of 
secretion holds. The single exception may possibly be due to a modification in the 
blood-flow through the gland during the time of collecting the saliva. The slowly 
secreted saliva contains a low percentage of salts, whether it is produced by a weak 
