148 
MESSRS. J. N. LANGLEY AND H. M. FLETCHER 
effect. It follows from this, since there is good ground for supposing that pilocarpin 
causes a secretion by stimulating the endings of the chorda tympani, that pilocarpin 
also is unable to stimulate strongly the gland. The high percentage of organic 
substance, then, in the saliva secreted slowly after repeated doses of pilocarpin must 
in the main be referred to the diminished blood supply to the gland. And it is 
proba,ble that the percentage of salts in the saliva, though higher than normal, is not 
very greatly so, because the stimulus to the gland is far from the normal maximum. 
In this way we should explain the results of Experiment 7, X. to XII. 
An instance of an increase in the percentage of salts caused directly by an increased 
stimulus, and not indirectly by increasing the rate of secretion of water, is, perhaps, 
given in Experiment 4. In sample VI., stimulation of the chorda has, in consequence 
of the previously injected atropin and pilocarpin, a barely appreciable effect on the 
rate of secretion of water, but it increases the percentage of organic substance and of 
salts above that of V., secreted previously to, and at the same rate as, VI. 
The Effect of a small dose of Atropin upon the Percentage Composition 
OF Saliva. 
It has been argued by one of us* that atropin paralyses “ secretory” and “trophic” 
fibres simultaneously. The results of Experiments 4 and 9 offer some confirmation of 
this. 
In both of these experiments a small dose of atropin is given, such that a stimula¬ 
tion of the chorda and injection of pilocarpin still produce some secretion. If atropin 
affected the “secretory” before the “trophic” fibres, the saliva obtained after atropin 
has been given should contain a high percentage of organic substance in proportion to 
its rate of secretion. This is not the case; on the contrary, the percentage of organic 
substance is small; the percentage is, in fact, so small that it, at first sight, appears 
as if the “ trophic ” fibres were affected more than the “ secretory ” fibres by the 
atropin. But we have seen that the secretion of water depends in part upon the 
amount of blood flow through the gland. In these experiments, after atropin had 
been given, the stimulation of the chorda and the injection of pilocarpin caused a 
copious blood flow, with but slight activity of the gland cells; hence, the secretion of 
water was abnormally increased. 
Sub-lingual Saliva. 
WertherI has shown that the sub-lingual saliva of the Dog contains a very high 
percentage of salts, and a rather low percentage of organic substance. The three 
analyses given by him are as follows :— 
* Langley, ‘ Journal of Physiology,’ vol. 9, 1888, p. 56. 
t Werthee, ‘ Archiv. f. d. ges. Physiol.,’ vol. 38, 1886, p. 298. 
