1905] BARNES—THE THEORY OF RESPIRATION 85 
both are valueless, since on the assumption upon which they are 
based neither can be interpreted. 
RESPIRATORY RATIO. 
Long before this sort of comparison was made, however, a 
voluminous literature arose which was concerned only with the 
ratio between the carbon dioxid given off and the oxygen consumed, 
, and how this ratio was influenced by temperature, by light, by this 
. q kind of food or that, by mere hunger, or by starvation. This ratio, 
, the so-called respiratory ratio or respiratory quotient, the plant 
physiologists really inherited from the animal physiologists, by whom 
_ __ it was devised with reference to the gaseous exchange that occurs 
in the lungs. This respiratory ratio has proved a veritable will- 
o’-the-wisp, leading investigators into a bog where their labors and 
____ their thinking were alike futile. For as a sign of what is going on 
within, the respiratory quotient is absolutely valueless, however 
interesting the facts in themselves may be. I could cite an indefi- 
nite number of investigations to indicate this. I select a few cases. 
As long ago as 1885, RUBNER showed! that the respiratory ratio 
varied in resting muscles at different temperatures. 
At 8.4° - - . . - “oe = 3.28 
2.2 - - - - - 1.01 
33-8 = a = = - 1.18 
38.8 - - - - - 0.91 
Von Frey and GruBeEr? showed that in a dog’s muscle, with 
artificial circulation, contractions are accompanied by an increase 
in the carbon dioxid added to the blood, but they found this increase 
variable (46-10 per cent.) and less than the corresponding absorption 
oj oxygen, so that the respiratory ratio became lowered during con- 
traction. Tuissor3 showed that the production of carbon dioxid in 
* Versuche iiber den Einfluss der Temperatur aster die fap cara des ruhendes 
Muskels. DuBois-Reym. Archiv fiir Physiol. 1885:3 
2 Versuche iiber den Stoffwechsel des Muskels. beer En Archiv fiir Physiol. 
1885: 533-562. 
3 Recherches sur i respiration musculaire. Arch. de Phys. Nori: et Path. V. 
6:838-844. Also, Variation des échanges gazeux d’un muscle extrait du corps. Op. 
et ser. cit. 7:641-653. 1895. 
