RELATION OF RATE TO PERCENTAGE COMPOSITION. 499 
He 1 showed, further, that in parotid saliva, obtained by stimulating 
Jacobson's nerve, there is similarly a decrease in the percentage of solids 
as the secretion goes on, and, no doubt, it is a general rule for all 
salivary glands. 
Kelation of the Kate of Secretion to the Percentage 
Composition of Saliva. 
Heidenhain 2 investigated the relations existing between the rate of 
secretion and the percentage composition of saliva. He showed that an 
increase in the rate of secretion was accompanied by an increase in the 
percentage of salts, and this whether the gland had secreted for a long 
time or for a short time. 
An example of this is given in the following experiment, in which the 
chorda tympani was stimulated with currents of varying strength, and a few 
c.c. of saliva collected in each case. The samples of saliva are arranged in the 
table in the order of their rate of secretion : — 
Order of sample 
5 
1 
7 
3 
8 
4 
2 
9 
6 
Mean rate of secretion 
per mm. 111 c.c. 
•15 
•18 
•19 
•22 
1-6 
2-0 
2 "2 
2-5 
3-2 
Percentage of salts . 
•34 
•29 
•25 
•32 
•37 
•58 
•44 
•57 
•58 
It will be noticed that the percentage of salts does not quite go hand 
in hand with the rate of secretion. But it is almost impossible to keep 
the rate of secretion constant during the time of collecting a sample of 
saliva, and to this the divergences may, in the main, be attributed. 
A closer relation between the rate of flow and the percentage of saliva was 
observed by Werther, 3 and by Langley and Fletcher. 4 Heidenhain found the 
percentage of salts to have an upper limit, with increased rate of secretion. 
This he gave as *5 to '6 per cent., though in one case - 66 per cent, was found. 
Beefier and Ludwig had earlier found in one case '78 per cent. Werther, and 
Langley and Fletcher found the maximum percentage to be '77. From the 
observations of the latter, it appears that the faster the rate of secretion, the 
less increase there is in the percentage of salts for a given increase in rate of 
secretion. This is indicated in the following table : — 
Rate of Secretion per 
Minute in c.c. 
Percentage of Salts. 
Increase in Percentage 
of Salts, correspond- 
ing to an Increase of 
0'1 c.c. per Minute 
in the Kate of Secretion. 
■400 
•4721 
•5I2J 
•04 
•500 
•760 
•599 
•033 
•900 
•616 
•012 
1-333 
•628 
•003 
1 Heidenliain, Arch. f. d. ges. Physiol., Born, 1878, Bd. xvii. S. 23. During eleven 
hours' stimulation the percentage of solids sank from 0"88 per cent, to - 49 per cent. 
2 Ibid., Bd. xvii. p. 1. Earlier observations on the same lines were given by him in 
1868 in his " Studien." 
3 Arch. f. d. ges. Physiol., Bonn, 1886, Bd. xxxviii. S. 293. 
4 Phil. Trans., London, 1889, p. 109. 
