840 ANIMAL HEAT. 
haemoglobin. 1 He found in two experiments that 100 volumes of 
blood absorbed respectively 20-2 and 18-5 volumes of oxygen, and 
produced thereby 14-63 and 14-91 calories. Now, the combustion of the 
oxygen with carbon would produce 97'65 calories, but, in the formation 
of oxyhemoglobin, only 14-8 calories were set free — that is, only a 
seventh of the heat of combustion would be set free in the lungs, the 
remaining six-sevenths in the tissues. M'Kendrick 2 and Bottomley 
have also been able, with a thermo-electric arrangement, to detect the 
heat produced by the union of haemoglobin with oxygen. 
The production of heat in muscle. — It has already been shown 
that during active muscular work the temperature of the body is slightly 
raised, although the loss of heat is at the same time greatly increased. 
The muscles must therefore be an important source of heat, and a 
further consideration will show that they are the chief source. The 
bulk of the body is chiefly composed of muscle ; thus, in a dog weighing 
11,700 grms., the muscles weigh 5400 grms., and the bones 2400 grins. 
(Bernard) ; 3 and even in a much less compact animal, a bat weighing 
19-94 grms., the muscles weigh 6-378 grms. (Pembrey). 4 
The production of heat as one of the phenomena of contraction 
in a single isolated muscle, and the relation of heat to work during a 
single contraction and during tetanus, are considered elsewhere. Here 
the muscles have to be examined as seats of heat production, not only 
during contraction, but during apparent rest; and, further, as regards 
the part they play in the production and regulation of the warmth of 
the body. 
The muscles, even when they have been removed from the body, are 
the seat of an energetic combustion (Humboldt, 5 Liebig, 6 Du Bois 
Beymond, Valentin, 7 Matteucci 8 ). The following comparative experi- 
ments were made 1 >y Paul Bert. 9 Different tissues were removed from 
a dog just killed, and the absorption of oxygen and discharge of carbon 
dioxide were determined during a period of twenty-four hours, at a 
temperature varying from 0" to 10° : — 
100 gnus, of muscle absorbed 50 -8 c.c. of oxygen, and discharged 56*8 c.c. of carbonic acid, 
brain ,. 45*8 ,, ,, 42*8 ,, 
,, kidney ,, 37"0 „ ,, 15-6 ,, 
,, spleen ,, 27'3 ,, ., 15*4 ,, 
>> testis ,,18-3 ,. „ 27'5 
(broken bone \ 7 . 
" ( and marrow J " » ° x >> 
Regnard 10 has shown that the respiratory exchange of isolated muscle rises 
and falls with the external temperature ; at 10° the discharge of carbon dioxide 
by 1 kilo, of muscle is 40 c.c. in one hour, at 25° it is 129 c.c, and at 35° it 
amounts to 294 c.c, hut above 40° the discharge decreases. 
1 See also Davy, "Researches," London, 1839, vol. ii. p. 168. 
2 Brit. Med. Journ., London, 1888, vol. ii. p. 338. 
3 "Lecons sur la chaleur animale," 1876, p. 1 40. 
4 Journ. Physiol., Cambridge and London, 1895-96, vol. xix. p. 485. 
5 " Versuche ueber die gereizte Muskel-und Nervenfaser," Berlin, 1797. 
6 Arch. f. Anat., Physio!, u. icissensch. Med.. 1850, S. 393. 
7 Arch, f.physiol. Hcilk., Stuttgart, 1855, Bd. xiv. S. 431. 
8 C'ompt. rend. Acad. d. sc, Paris, 1856, tome xlii. p. 648; Ann. dc chim. et phys., 
Paris, 1856, tome xlvii. p. 129. 
9 " Lecons sur la physiol. comparee de la respiration," 1870, p. 46. 
10 "Eecherches expe'rimentales sur les combustions respiratoires," Paris, 1879, p. 23. 
