PRODUCTION OF HEAT IN GLANDS. 843 



Waller l estimates it at 20,000 kilogrammetres, and Nicolls 2 at 54,000 

 kilogrammetres. 



The production of heat in glands. Glands are the seat of active 

 chemical changes, accompanied by a production of heat, but during 

 activity their blood supply is augmented, and the increased temperature 

 arising from this cause often masks the heat produced by the activity 

 of the glands. 



The submaxillary gland is an instance in which the activity of the 

 tissue is accompanied by a greatly increased blood flow. Ludwig and 

 Spiess 3 found by the thermo-electric method that the submaxillary 

 saliva of a dog was 1 to 1'5 warmer than the blood in the carotid 

 artery. Bernard 4 ligatured the blood vessels of the gland, and found that 

 stimulation of the chorda tympani still produced a slight rise in temper- 

 ature, whereas excitation of the sympathetic produced a slight fall. The 

 temperature in degrees is not stated, but Bernard brings these observations 

 forward as additional arguments in favour of frigorific nerves. Morat 5 

 states that he has been able to confirm Bernard's results ; Heidenhain, 6 on 

 the other hand, observed a rise in temperature when the sympathetic was 

 stimulated. Eecently, Bayliss and Hill 7 have carefully investigated 

 the question of the formation of heat in salivary glands ; they used both 

 the thermo-electric method and Geissler's thermometers. Their results 

 led them to the following conclusions : The temperature of the gland 

 and tissues around it is almost as high as that of the aortic blood ; the 

 saliva is not warmer than the gland and tissues around the duct, and no 

 formation of heat can be directly determined in the submaxillary gland 

 by any known method of measuring variations in temperature. On 

 stimulation of the chorda tympani, the temperature of the saliva never 

 rose higher than the temperature of the aortic blood. No doubt the 

 gland produces more heat during activity, but, on account of the small 

 size of the gland, and the rapid circulation, the difference cannot be 

 shown. 



The intestines and liver. According to Bernard, 8 the blood coming 

 from the intestines is raised in temperature during digestion, the tem- 

 perature of the blood in the portal vein being two- or three-tenths of a 

 degree warmer than that of the abdominal aorta. Bernard also found 

 that the liver was the warmest organ in the body, that the blood of the 

 hepatic vein was higher than that of the portal vein, and showed a still 

 further increase during digestion. 



Stimulation of the splanchnic, or of the vagi nerves, produces no 

 calorific or frigorific effect in the temperature of the liver. 9 



1 " Human Physiology," 1893, 2nd edition, p. 75. 



2 Journ. Physiol., Cambridge and London, 1896, vol. xx. p. 407. 



3 Sitzungsb. d. k. Akad. d. Wissensch., Wien, 1857, Bd. xxv. S. 584 ; Ludwig, Wien. 

 med. Wchnschr., 1860, Nos. 28 and 29. 



4 " Lemons sur la chaleur anirnale," 1876, p. 428. 



5 Arch, de physiol. norm, etpath., Paris, 1893, tome xxv. p. 285. 



6 Stud. d. physiol. Inst. zu Sreslau, Leipzig, 1868, Bd. iv. 



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



8 " Lemons sur la chaleur animale," 1876, p. 190. See also this article, p. 809; Braune, 

 Virclwws Archiv, 1860, Bd. xix. S. 470, 491. 



9 Waymouth Reid, "Proc. Phys. Soc.," Journ. Physiol., Cambridge and London, 1895, 

 vol. xviii. 



