352 PRINCIPLES OF ANIMAL NUTRITION. 
extended citation of authorities here. Some of Rubner’s* more 
recent results, however, are of interest as showing the delicacy of 
the reaction. The experiments were made on fasting dogs in a 
state of complete rest, the heat production being computed from 
the total metabolism of carbon and nitrogen: 
Tempera- Heat Production per 
ture, Deg. C. Kg. in 24 Hours. 
1358) se ikaeadateteess 78.68 Cals. 
Weld Osea ain en aa Sie es 74.74 
LU ce ete ees eee 69.78 “ 
WS; ZO sirsuseuroarinceheett ale 67.06 “ 
LL Sicteese nes vee ew ees 40.60 “ 
LOO) sa aeecsecniatanlae 39.13 “ 
1) 15.9...... arena; 35.99 “ 
Th Deteneeegan htc 35.22 “ 
Ss A tua wee an pce nee 39.65 “ 
Til 19 Detcac ee was 35.10 “ 
Qh Bere opi triahiias Oh ives eee. 30.82 “ 
This method of regulation of the body temperature is often briefly 
designated as “chemical” regulation. 
Just how the additional generation of heat is effected is not so 
clear. From the fact that the muscles are the seat of a very large 
part of the heat production of the body we should naturally be 
inclined to look to them as the source of the increase. In quite a 
number of experiments on man, of which those of A. Loewy + and 
of Johansson { may be especially mentioned, a stimulation of the 
heat production with falling temperature was only observed when 
there was visible muscular action, such as shivering, while in the 
other cases only the “physical” regulation occurred. Any contrac- 
tion of the muscles would of course be a source of heat, but the in- 
crease with falling external temperature has been repeatedly observed 
with animals in the absence of this obvious cause. Whether in 
such cases there is an increase in the tonus of the muscles, involv- 
ing an increase in their metabolism, or whether, through some 
form of reflex stimulation, the rate of oxidation is accelerated 
* Biologische Gesetze, p. 10. 
t Arch. ges. Physiol., 46, 189. 
¢ Skand. Arch. f. Physiol., 7, 123. 
