7 2 o CHEMISTR Y OF RESPIRA TION. 
was about 24 per cent, in the carbon dioxide, and 17 per cent, in the 
oxygen. Sodium chloride and sodium bicarbonate had no effect on the 
intestines or upon the respiratory exchange. Lbwy suggests that the 
therapeutic value of the waters at Carlsbad and Marienbad, in cases of 
disordered metabolism, may be partly due to this stimulating effect of 
sodium sulphate. 
The influence of the size of the animal upon the respiratory- 
exchange. 1 — The smaller an animal the greater is its surface in relation 
to its mass, for the surface increases as the scpuare, the mass as the cube. 
Now, small mammals and birds have a temperature equal to or even 
higher than that of large animals of the same classes ; and, on account of 
the relatively greater surface which they expose for the loss of heat, 
they must have a relatively far greater production of heat than the 
large animals, for there is generally no marked difference in the pro- 
tective coat of fur or feathers. Heat is produced by a process of 
combustion in the tissues, and the respiratory exchange is a measure, 
although it may not lie an absolutely exact one, of this combustion. 
Theoretically, therefore, a much more vigorous respiratory exchange 
should exist in the smaller warm-blooded animals. The experiments of 
many observers, especially of Letellier, 2 Eegnault and Eeiset, 3 Pott, 4 and 
Eichet, 5 have shown that such is the case, not only for animals of the 
same species, living upon similar diet and having similar habits, but 
also for animals of different species, with very different diets and 
habits. 6 
Paul Bert 7 has shown that this difference in the rate of metabolism 
in small and large animals has become habitual, for it persists even 
when the animals are put under abnormal conditions of such a kind 
that the loss of heat is relatively the same ; in such an experiment a 
pigeon absorbed 234 c.c, of oxygen per 100 grms. of its body weight, and 
a sparrow 467 c.c. of oxygen. 
A series of experiments have been made by Eichet 8 upon thirty-eight 
dogs of different sizes, their weights ranging from 2*2 to 28 kilos., and 
the results show that the output of carbon dioxide bears a very constant 
relation to the surface of the body, 0*0027 grins, per hour for each 
square centimetre of surface. A similar relation holds good for the 
intake of oxygen, the respiratory quotient being 0-748. This difference 
in metabolism is controlled by the nervous system, for it was found, 
in eighteen dogs of different sizes, anaesthetised with chloral, that the re- 
spiratory exchange was proportional to the weight of the body, 0-640 to 
0-694 grms. C0 2 per kilo, and hour. A somewhat similar series of 
observations, made upon birds 9 of different sizes and species, gave 
similar results. 
1 For a discussion of this subject, see paper by Hoessliu, Arch. f. Physiol., Leipzig, 
1888, S. 323, where numerous references are given ; Rubiier, Ztschr. f. Biol., Munchen, 
1883' Bd. xix. S. 535. 
2 Ann. de chirn. ctphys., Paris, 1S45, Ser. 3, tome xiii. p. 478. 
3 Ibid., Paris, 1849, Ser. 3, tome xxvi. p. 299. 
4 Lanclwirthsch. Versuchsstat., Bd. xviii. S. 81. 
5 Arch, de physiol. norm, ct path., Paris, 1890, tome xxii. pp. 17, 490 ; 1891, tome 
xxiii. p. 74. 
6 See tables, pp. 706-708. 
7 "Lecons sur la physiol. comp. de la respiration," Paris, 1870, p. 503. 
8 Compt. rend. Acad. d. sc, Paris, 1S89, tome cix. p. 190 ; Arch, dc physiol. norm, ct 
path., Paris, 1890, tome xxii. p. 17. 
9 Arch, depihysiol. norm, etpath., Paris, 1890, tome xxii. p. 490. 
