ELECTRICAL CHANGES IN THE GLANDS. 517 



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, on 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 Journ. PhysioL, Cambridge and London, 1894, vol. xvi. p. 351. 



- 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. Journ. Anat. and HistoL, 

 1887, vol. iv. The ingoing current of the skin of the frog was discovered by du Bois Rey- 

 mond in 1857. He attributed it to the glands present in the skin (cf. " Untersuch. u. 

 thierische Elektricitat," I860. Bd. ii. 



4 Journ. PhysioL, Cambridge and London, 1887, vol. viii. p. 86. 



