798 ANIMAL HEAT. 
was 20° ; the warmth, however, delayed the onset of torpidity by two 
months, and made it less profound. 1 Further, it is found that in some cases 
hibernation takes place in the dry hot season ; thus there is in Madagascar an 
animal, closely allied to the hedgehog, and called the tanrec (Centetes 
ecaudatus), which buries itself and becomes lethargic in the dry season, when 
its insect food is inaccessible. 2 The reptiles and many of the invertebrate 
animals of tropical climates seek their hiding-places and fall into a state of 
torpor during the dry season, when the heat is most intense. Torpidity in 
dormice and hedgehogs may be delayed or prevented by a plentiful supply of 
food. 3 
Want of food and cold seem to be the most important factors, but there 
must be some other condition, at present unknown, to explain the cases of 
marmots hibernating during the summer. It is certain that many species of 
animals which become torpid in one country do not become so in another. 
This fact, according to Barton, 4 is very noticeable in the United States, for 
many species which hibernate in Pennsylvania and other more northern 
parts of the country, do not hibernate in the Carolinas and other southern 
parts of the continent. Attempts have been made, but without success, to 
find anatomical differences, especially as regards the blood vessels of the brain, 
which would account for hibernation. 5 
The most recent theory is that of Dubois, 6 who maintains that hibernation 
is caused by an autonarcosis with carbon dioxide. In support of this theory 
he adduces the following facts, namely, the accumulation of carbon dioxide in 
the blood, and the production of torpidity in marmots exposed to an atmo- 
sphere containing about 40 per cent, of carbon dioxide. 
The Influence of Various Conditions upon the Temperature of 
Man and Other "Warm-blooded Animals. 
Numerous observers have insisted upon the occurrence of small 
variations in the temperature of healthy men and animals, and have 
shown by experiments that these variations are due to several causes. 
Influence of day and night. — The temperature of man is subject 
to slight daily variations ; it rises during the morning and afternoon, 
it fails during the evening and early part of the morning. Upon 
the points of maximal and minimal temperature, and the range of 
variation, the results differ considerably, as the table on p. 799 
shows. 
It will be seen from these results that there is more agree- 
ment upon the time of the minimal daily temperature than upon that 
of the maximum. The causes of this difference are mainly two : in the 
first place, there appears to be a rise and then a fall in temperature 
before the ascent to the maximum begins. Thus Barensprung found a 
rise in the early morning to 11 a.m., then a fall to 2 p.m.; and Damrosch 
observed that the temperature rose from 7 a.m. to 10 A.M., and then fell 
1 Berthold, Arch.f. Anal., Physiol, n. loissensch. Med., 1S37, S. 63. 
2 This statement "of Cuvier and Bruguiere is contested by Brown- Sequard ("Ex- 
perimental Researches applied to Physiology and Pathology," New York, 1851, p. 25), who 
maintains that the tanrec hibernates in the winter season, when the external temperature 
is from 15 to 23 degrees. 
3 Reeve, "An Essay on the Torpidity of Animals," 1809. 
4 Trams. Am. Phil. Soc, Phila., 1799, vol. iv. p. 121. 
5 Mangili, Arch. f*d. Physiol., Halle, 1808, Hd. viii. S. 410 ; Saissy, Deutsches Arch, 
f. d. Physiol., Halle.' 1817, Bd. iii. S. 136. 
6 Compt. rend. Acad d. se., Paris. 1895, tome exx. p. 458 ; Oompt. rend. Soc. dc biol., 
Paris, 1895, 3e Mars. 
