WARM-BLOODED AND COLD-BLOODED ANLMALS. 787 
for three or four minutes in the rectum or vagina; 1 it should be kept in 
position for a minute or two after the mercury has become stationary. 
Different values have been given by various observers for the 
temperature in the mouth, axilla, and rectum; these will be critically 
examined later, but at present it may be stated that the temperature 
in the rectum is generally about three- or four-tenths higher than that 
in the axilla or mouth. Under certain circumstances, however, this 
relationship is altered. Thus Bosanquet 2 found that, although the 
temperature in the rectum was almost invariably higher than that in 
the mouth, the average difference being four-tenths, yet on some occa- 
sions, as immediately after eating, the temperature in the mouth 
exceeded that in the bowel; while on others, as during vigorous 
exercise, the heat of the mouth sank considerably, e.g. to 35 0- 6 (96° F.), 
that of the rectum rising to 37°'7 (99°-8) or 37°-8 (100°). Violent 
exercise was found by Davy 3 to lower the temperature in the mouth, 
and raise that in the axilla. The probable explanations of these differ- 
ences are that vigorous exercise would, by the increase of respiration, 
cool the mouth, and by increasing the vascularity of the axilla raise the 
heat in that part. The increase in the temperature of the mouth 
immediately after eating is probably due to the increase in the blood 
supply and activity of the muscles and glands in that cavity. 
In order to obtain the maximal temperature of the interior of the body, 
Kronecker and Meyer 4 used small bulbs of mercury, made according to 
the principle of Dulong and Petit's outflow thermometer. The animal 
was made to swallow the small bulb, which, after evacuation by the 
bowel, was placed in water gradually warmed until the mercury ex- 
panded to the point of outflow; the temperature of the water repre- 
sented the maximal temperature of the body. It was found by this 
method that the maximal temperature of a dog was 39° - 2 and that of a 
rabbit 40 o- 2, the rectal temperatures varying respectively from 37° - 8 to 
38° - 2, and 37°"0 to 37°"9. Special thermo-electric methods will be 
mentioned in the discussion of surface temperature. 
Warm-blooded and cold-blooded animals. — An important differ- 
ence in temperature exists between the higher and lower animals. Those 
animals which are high in the scale of evolution, such as birds and 
mammals, have a high temperature, which is fairly constant and in- 
dependent of the temperature of the surrounding air. The lower 
animals, on the contrary, have a temperature dependent upon, and only 
slightly above, that of their surroundings, and thus liable to considerable 
variations. This difference between the two classes is expressed by 
the terms " warm-blooded " and " cold-blooded " animals. The classifica- 
tion, however, is not absolutely exact, for there are mammals, such as 
the marmot, hedgehog, bat, and dormouse, which are in an intermediate 
position ; in warm weather these animals have a high temperature, 
which is fairly constant and independent of their surroundings, but in 
winter they become inactive, they hibernate, and their temperature 
falls and varies with that of their surroundings. On the other hand, 
there are bees, animals of a much lower order, which have and maintain 
1 Crombie, Indian Ann. Med. Sc, Calcutta, 1873, vol. xvi. pp. - r )54-559. 
2 Lancet, Loudon, 1S95, vol. i. p. 672. 
3 "Researches," London, 1839, vol. i. p. 199. 
4 Arch./. Physiol., Leipzig, 1878, S/546. 
