THE, MECHANISM : OF TIssuz 
RESPIRATION 
By H. M. VERNON, M.A., M.D. 
Fellow of Magdalen College, Oxford 
Ir is a fundamental property of all living organisms to be 
continually giving off carbon dioxide, and for all except 
certain bacteria and parasites to be continually absorbing 
oxygen. With these processes of respiration most of the 
so-called vital properties of protoplasm are so _ intimately 
bound up that, could we unravel them in their entirety, we 
should be not far from solving the mystery of life itself. 
How very remote we are from even a partial solution of the 
problem will be evident from the pages of this article, but 
we have at least made some progress towards it within 
recent years. 
And firstly, how far are the carbon-dioxide-producing 
powers and oxygen-absorbing powers of living tissues de- 
pendent on one another? It would seem at first sight that 
they are but little related, for it was shown by Spallanzani 
in 1803, and since then by Johannes Miller and others, that 
animals such as the frog continue to exhale CQO, even 
when entirely deprived of oxygen. In 1875 Pfliiger repeated 
these observations, and he found that frogs, when kept in 
nitrogen containing no trace of oxygen, continued to give 
out CO, for several hours, at a rate but little inferior to 
that exhibited by frogs kept in air. Aubert made some direct 
comparisons of the CO, discharge of frogs kept in air or 
in nitrogen in a large glass cylinder over mercury. The 
experiments lasted four hours as a rule, and they were 
made at temperatures varying in different cases from 3°6° to 
160 
. 
