TEMPERATURE OF THE SKIN. 829 



It will be seen from the two tables that the results lead to directly 

 opposed conclusions, but a critical examination shows that the correct 

 one is probably that the blood in the right ventricle is 0*1 to 0'2 

 warmer than that in the left. In many of the older experiments the 

 methods were inexact, the chest was opened and the heart exposed ; 

 the right ventricle, on account of its thin walls, would cool more quickly 

 than the left, as shown experimentally by G-. Liebig. The most exact 

 method appears to be the insertion of delicate thermometers or thermo- 

 electric needles down the jugular vein and the carotid artery into the 

 right and left ventricle respectively. This method was employed by 

 Heidenhain and Korner 1 in numerous experiments upon dogs, with the 

 result that in all but one of the observations the right side of the heart 

 was warmer than the left. Thus in one case the difference was '6, 

 in two '5 to '6, in three *5, in five '3 to -4, in twenty-seven '2 to "3, 

 in thirty-six -1 to '2, in twenty-one '15, in one case no difference at 

 all. To determine whether the inspiration of cold air was the cause of 

 this difference, Heidenhain and Korner made comparative experiments, 

 employing for artificial respiration in the one case cold air (17), and in 

 the other hot air (40) saturated with moisture. The difference still 

 remained, and it was therefore concluded that respiration was not the 

 cause ; cold air when inspired is warmed and saturated with moisture 

 before it reaches the alveoli ; 2 further, in passing through the upper 

 parts of the respiratory tract, the cold air would cool the blood in veins 

 going to the superior vena cava and thus to the right side of the heart. 

 These observers conclude that in the dog the right ventricle is warmer 

 than the left, because its walls lie nearer to the liver and other 

 abdominal organs, which have a high temperature, while the left 

 ventricle is surrounded by lung. It was found, in fact, that the 

 difference in temperature could be reduced to a minus quantity by 

 artificially lowering the temperature of the abdominal cavity. Bernard 

 does not accept this explanation as satisfactory ; for he points out that 

 in Bering's observation the right ventricle was half a degree warmer 

 than the left, although the heart, owing to a congenital defect, was 

 outside the thorax. 



The temperature of the skin. The temperature of the human skin 

 shows differences in different parts of the body, and is also subject to 

 variations due to alterations in the external temperature, the amount of 

 natural or artificial covering, the vascularity of the parts, and the 

 amount of evaporation taking place from the surface. Apart from 

 these variations, there is a difficulty in measuring accurately the 

 temperature of the skin ; a mercurial thermometer applied to the skin 

 receives heat from the surface in contact with the skin, and loses 

 heat from the surface exposed to the air. If, on the other hand, 

 the thermometer is covered with a non-conductor, or the external 

 temperature is raised, then the heat of the part of the skin observed 

 is increased. To overcome these difficulties, thermo-electric methods 

 have been used. 3 



The disadvantages of these thermo-electric methods are the complexity 



1 Arch.f. d. gcs. PhysioL, Bonn, 1871, Bd. iv. S. 558. 



2 See "Chemistry of Respiration," this Text-book, vol. i. p. 754. 



a Christian! and Kronecker, Arch.f. PhysioL, Leipzig, 1878, S. 334; Kunkel, Ztsclir. f. 

 Biol., Miinchen. 1889, Bd. xxv. S. 55 ; Masje, Virchow't Archiv, Bd. cvii. S. 17, 267 ; 

 Geigel, Ferhandl. d. phys.-med. Gesellsch. in Wiirzburg, 1888, N. F., Bd. xxii. S. 8 ; 

 Stewart, Stud. PhysioL Lab. Owens Coll., Manchester, 1891, vol. i. p. 100. 



