ON THE SECRETION OF SALIVA. 
11 L 
of which is constant. During the time of collecting the saliva the rate of secretion 
varies ; in two successive samples the variation in rate will almost certainly he not 
quite the same, and, in consequence, the relation between the percentage of salts and 
the rate of secretion will he obscured. The variations in the rate of secretion w^hich 
occur when the chorda tympani is stimulated are partly due to normal causes, and 
partly to abnormal causes brought about by the exposure of the nerve. Normally, 
when the chorda tympani is stimulated the rate of secretion rapidly rises to a 
maximum, and then slowly declines. When the nerve is dissected out, its irritability 
gradually falls, and if, as often is the case in dissecting out the chorda, some lobules 
of the subdingual gland are cut through, so that their secretion oozes out and soaks 
into the nerve, its irritability falls rapidly ; in either case it may happen that, in 
collecting a sample of saliva, the stimulus previously causing a rapid secretion causes 
only a slow one; on seeking to correct this by increasing the sti’ength of the stimulus 
the secretion often becomes over-rapid, and a mixture of salivas secreted at very 
different rates is the result. 
Further, as Heidenhain has pointed out, a variation in rate is brought out on 
chorda stimulation by the unequal irritability of the nerve along its course ; a very 
slight shifting of the electrodes in either direction may cause a considerable variation 
in the rate of secretion. In Experiment 2, No. I., for example, the electrodes were 
placed on the part of the chorda adjoining the lingual nerve, but the number of drops 
of saliva produced by stimulating for 30 seconds varied from 1 to 4 with the index of 
the secondary coil at 12 cm., and from 3^ to 8 with the index of the secondary coil 
at 11‘5 cm. 
Variations in the Percentage of Salts in Chorda Saliva obtained under 
Normal Conditions. 
Our first experiments were to try whether, by noting the variations in the rate of 
secretion during the time of collecting each samjile of saliva, we could account for 
any variation that might occur in the percentage of salts. But, as we had no doubt of 
the general truth of Heidenhain’s conclusions, we performed the experiments under 
somewhat different conditions from those of Heidenhain, so as to still further test 
these conclusions. 
Unless otheriuise mentioned the following procedure loas adopted in each of the Experiments. 
Morphia in 5 per cent, solution was injected sub-cutaneously; in half to three-quarters of an hour, 
when severe pinching of the skin produced no movement, the animal was given chloroform. A three- 
way tube was tied in the trachea, one limb of the tube being’ connected at intervals with a bottle con¬ 
taining a mixture of chloroform and ether. 
The lingual nerve was ligatured and cut peripherally of the point where it gives off the choi’da 
tympani; lifting this up, the central end of the lingual nerve and then the chordo-lingual were isolated 
