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II. On the Secretion of Saliva, chiefiu on the Secretion of Salts in it. 
By J. N. Langley, M.A., F.R.S., Fellow of Trinity College, and H. M. Fletchee, 
B.A., Trinitji College, Cambridge. 
Receirecl August 17,—Rear! November 15, 1888. 
Previous Observations. 
The earliest observations on variations in percentage of salts in saliva with which we 
are acquainted, are those of Ludwig and Becher,'" in 1851. They analysed successive 
portions of saliva, obtained under different conditions, from the submaxillary gland of 
the Dog. 
Three experiments were made on the effect of protracted secretion ; in two of these 
the percentage of salts sank in the successive portions of saliva, but in the remaining 
one, the third and fourth samples of saliva contained a rather higher percentage of 
salts than the second and first samples. The total amount of saliva collected in this 
case was 48'5 grm. 
Three experiments were made in the following manner;—Saliva was collected, then 
blood withdrawn from the animal, water injected in the place of the blood, and saliva 
again collected ; in two of these experiments the defibrinated blood was re-injected, 
and a further portion of saliva obtained. In all these cases the percentage of salts in 
the saliva sank during secretion. 
Lastly, in one experiment fourteen samples of saliva were obtained, in all 177 grm.; 
and twice during the course of the experiment 150 grm. of a 7‘33 per cent, solution 
of sodium chloride were-injected. After the first injection there was a rise in the 
percentage of salts in the saliva; after the second injection there was a fall in the 
percentage of salts below that of tlie first sample, A few only of the samples of 
saliva were analysed. 
These observations showed that during secretion the percentage of salts falls in 
most, but not in all, cases; and they indicated that the percentage of salts depends 
upon the condition of the gland with regard to fatigue. 
Heidenhain t placed the matter on a different basis. He analysed successive small 
quantities of saliva, secreted at different rates, and found that, up to a certain limit, 
* Ludwig and Becher, ‘Zeitschr. f. rat. Med.,’ New Series, vol. 2, 1851, p. 278. 
t Heidenhain, ‘ Studien des physiol. Insbituts zu Breslau,’ Part 4, 1868, pp. 30 et. seq., and ‘ Ai'chiv 
f. d. gesannnte Physiologie,’ vol. 17, 1878, p. 3. 
7 . 3.89 
