THE MECHANISM OF TISSUE 

 RESPIRATION 



By H. M. VERNON, M.A., M.D. 

 Fellow of Magdalen College, Oxford 



It 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 Muller and others, that 

 animals such as the frog continue to exhale C0 2 even 

 when entirely deprived of oxygen. In 1875 Pfluger repeated 

 these observations, and he found that frogs, when kept in 

 nitrogen containing no trace of oxygen, continued to give 

 out C0 2 for several hours, at a rate but little inferior to 

 that exhibited by frogs kept in air. Aubert made some direct 

 comparisons of the C0 2 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 



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