ELECT RK ' / /. CHANGES IN THE GLANDS. 5 1 7 
stimulation of the sympathetic caused a fall of temperature in the gland of the 
same side. He concluded that calorific nerve-fibres are present in the chorda 
tympani, and frigorific nerve-fibres in the sympathetic; but there is nothing 
in the account to show that the results were not due simply to a variation in 
the blood supply. 
These results till recently passed unquestioned. But Bayliss and 
Hill, 1 on testing them, both by the thermo-electric and the thermometric 
methods, never found the chorda saliva to be warmer than the arterial 
blood. Their experiments differed in some points of method from 
Ludwig's. On one of these they consider the difference in result de- 
pends. The thermo-electric junction or the thermometer was pushed up 
the femoral artery into the aorta, so that it was exposed to the full 
current of blood. Bayliss and Hill consider that in Ludwig's experiment 
the temperature observed was less than the real temperature of arterial 
blood, so that, mi stimulating the chorda tympani, the saliva secreted, 
though of a higher temperature than that recorded for the blood, was 
not of a higher temperature than that of the blood actually supplied to 
the gland. 2 And they came to the conclusion that no formation of heat 
in the submaxillary gland can be determined directly by any known 
method of measuring variations in temperature. 
Supposing for a moment that this conclusion is correct, it does not 
of course mean that no heat is formed in the gland during secretion, but 
simply that the heat — undoubtedly set free by the chemical changes — is 
insufficient to cause an appreciable rise of temperature in the considerable 
mass made up of the saliva, the gland, and the blood flowing through the 
gland. But the main question can hardly be regarded as settled. For 
the tissues in the neighbourhood of the gland artery and of the duct are 
— at any rate, after placing a cannula in the duct and preparing the 
chorda tympani — at a lower temperature than the aortic blood. So that 
both the blood to the gland and the saliva secreted tend to become 
cooled. And thus it would be possible for the recorded temperature of 
the saliva to be less than that of aortic blood, although the temperature 
of the saliva secreted were higher than that of the blood supplied to the 
gland. 
Electrical Changes in the Salivary Glands. 
The electrical currents of the salivary glands of the dog and cat 
have been made the subject of observation by Bayliss and Bradford, 3 and 
by Bradford. 4 In such experiments, one non-polarisable electrode is 
placed upon the outer convex surface of the gland, and the other upon 
the gland close to the hilus. It is convenient to use Hermann's nomen- 
clature for the currents which may be observed. When the outer 
surface of the gland is positive to the hilus, so that the direction of the 
current in the galvanometer circuit is towards the hilus, and in the 
1 Joum. Physiol., Cambridge and London, 1891, vol. xvi. p. 351. 
2 It may be mentioned that the blood temperatures recorded by Bayliss and Hill are in 
nearly all cases less than those recorded by Ludwig, but no definite conclusion can be 
drawn from this. 
3 Proc. Roy. Soc. London, 1886, No. 243, p. 203 ; Internal. Joum. Anat. and Histol., 
1887, vol. iv. The ingoing current of the skin of the frog was discovered by du Bois Ray- 
mond in 1857. He attributed it to the glands present in the skin (cf. " Untersuch. ii. 
thierische Elektricitat," I860, Bd. ii. 
4 Joura. Physiol., Cambridge and London, 1887, vol. viii. p. 86. 
