THE MECHANISM ‘OF - TISSUE) .RESPIRATION. 16% 
195°C. For purposes of comparison the results obtained have 
been grouped together and means taken. 
FROGS KEPT IN AIR. FROGS KEPT IN NITROGEN. 
Number of CO, per hour Number of CO, per hour 
Experiments. Temperature. per 1 ilogram. || Experiments. Temperature. per Kilogram. 
5 3°6" ta 9:6" 2A C.e 9 BiG: ta. Gis: 24 C.C. 
4 10D". |43 EAS 46 c.c. 3 BE 3t ys 13S) 43 C.C. 
2 ISO), Io 5. 72 Cee 8 TO! 45 {1925 - 7 OCC 
From these mean results we see that the CO, discharge of the 
frogs kept in nitrogen was practically as great as that of frogs 
kept in air, and that it was influenced to the same extent by rise 
of temperature. The lack of oxygen, though at first producing 
no obvious effect either in the CO, discharge or the vitality of 
the frogs, did so after a time, and the higher the temperature at 
which the experiment was carried out the sooner were the effects 
produced. The movements of the frogs became gradually 
feebler, and then ceased, though the heart continued to beat 
long after the nervous system was completely paralysed, and 
the CO, discharge continued to some extent even after cessation 
of heart-beat. At a temperature slightly above zero the frogs’ 
movements continued as long as seven days. At 7° C. they 
continued for eight hours on an average, and at 12° for five 
hours; but at 21° they ceased in seventy-two minutes, and at 
27° in twenty-five minutes. Though the CO, discharge persisted 
for longer than these periods, it slackened off very quickly at 
the higher temperatures, and so it was found that the /ofal 
volume of CO, given off by the frogs was practically independent 
of the temperature. There seems to be a more or less fixed 
volume of CO, in the tissues of the frog, and this volume can 
either come off very slowly at a low temperature, or rapidly at 
a high one. Aubert did not attempt to fix the volume exactly, 
but he found that whether the frog were kept in nitrogen for 
1,383 minutes at 7.9, for 575 minutes at 11°8°, for 110 minutes 
at 22°8°, or for 35 minutes at 27°5°, it almost always gave 
off about 200 c.c. of CO, (reckoned per kilogram of body 
weight). 
The CO, discharge in a nitrogen atmosphere has been 
measured also in the case of a snail (Limax agrestis) and a 
caterpillar (Tenebrio molitor). Thunberg, who carried out these 
II 
