144 
MESSRS. J. N. LANGLEY AND H. M. FLETCHER 
The considerable increase in salts in IV. is, we think, due to some interference with 
the circulation through the gland, for this contains a higher percentage of organic 
substance than the more rapidly secreted saliva III. 
General Remarks on the Effect on the Secretion of Salts and Injecting 
Salt Solution into the Blood. 
We have seen that, when the volume of the blood is increased to any considerable 
extent by salt solution varying from '2 to 2 per cent., the rate of secretion for a given 
stimulus is increased. This we take to be due to a larger quantity of blood passing- 
through the gland ; and from this, together with the fact that bleeding decreases the 
rate of secretion, we conclude that, within certain limits, the amount of water secreted 
for a given stimulus—with a given irritability of the gland—varies directly with the 
amount of blood passing through the gland. 
The increased secretion of water brought about by increased blood-flow is accom¬ 
panied, unless, perhaps, when the blood is excessively diluted, by an increase in the 
secretion of salts. The extent of the increase depends upon the percentage of salts 
in the blood ; if the percentage of salts in the blood be sufficiently diminished, the 
increase in the amount of salts secreted does not keep pace with the increase in the 
secretion of water, and, consequently, the percentage of salts in the saliva falls. If 
the percentage of salts in the blood be sufficiently increased, that of the saliva will 
also be increased. 
We have made no direct experiments upon the effect of increasing the volume of 
the blood without altering the percentage of salts in it; but we are inclined to think, 
from a consideration of Experiment 4, that in such case, and with a given stimulus, 
the secretion of water would be more increased than the secretion of salts ; that is, 
that the percentage of salts would increase with the increase of flow, but rather less 
than normally. 
In Experiment 4, the saliva is obtained before and after giving a small dose of atropin. After snob a 
dose, stimulation of the chorda tympani •with strong induction shocks, or the injection of large doses of 
pilocarpin, produces on the gland the effect of a weak stimulus only, in so far that the secretion of water 
is slow, and the percentage of organic substance and of salts in it is small. But the stimuli are still 
able to produce a maximal, or nearly maximal, effect on the small arteries. Hence, then, in Experi¬ 
ment 4, the samples of saliva III. to VI. inclusive are obtained under conditions of more copious blood 
supply than normally accompanies a weak stimulation of the gland. Taking I. as a standard, we think 
that III. to VI. contain a smaller percentage of salts than corresponds with their rate of secretion. 
Variation in the Percentage of Salts in Saliva Secreted under the 
Influence of Pilocarpin. 
In comparing samples of saliva secreted at different rates under the influence of 
pilocarpin, we, of course, leave out of account those in which one sample is secreted 
