268 SCIENCE PROGRESS 



many differences of character, and that it must be a very long 

 time before we can hope to unravel all the intermediate stages. 

 We have seen that under some conditions a considerable absorp- 

 tion of oxygen may occur without any contemporary production 

 of CO,, but in these experiments the minced tissue had lost 

 its vitality. The writer J found that a loss of C0 2 -producing 

 power but continuance of oxygen absorption power can be 

 induced in still living tissues. If intact kidneys be perfused 

 for half an hour with saline containing o'i to 0-5 per cent, of 

 formaldehyde, the oxygen absorption of the tissues is diminished 

 to some extent, but the C0 2 production is diminished very much 

 more, and for the first two hours or so after the poisoning 

 respiratory quotients of o - 4 or less are obtained. Subsequently 

 the kidneys gradually recover, and after ten hours' continuous 

 perfusion may have nearly as great a CO, production and 

 oxygen absorption as normal kidneys. Lactic and nitrous acids 

 have an analogous though less marked effect, whilst alkalis 

 likewise reduce the C0 2 production of the tissues more than 

 their oxygen absorption, but do not permit of much recovery 

 of respiration on subsequent perfusion. Other poisons, such 

 as hydrocyanic acid, sodium fluoride, and acid sodium sulphite, 

 reduce both the oxygen absorption and C0 2 production of the 

 kidneys to the same extent, but after some hours' perfusion 

 with fresh saline there may be complete recovery. Now all 

 these substances are well known to have the power of entering 

 into loose combinations with aldehyde groupings, so it seems 

 probable that such groupings exist in living tissues, and that 

 these poisons enter into temporary combination with them and 

 so stop respiration processes. 



From the foregoing brief account of the present state of 

 our knowledge on the biochemistry of respiration, it will be 

 seen that recent research points to its being in the main 

 dependent on intracellular enzymes. In some organisms it 

 is entirely a hydrolytic process, unaccompanied by any oxidation 

 whatever, but in the great majority of organisms it is partly 

 hydrolytic and partly oxidative. Whether the main processes 

 of respiration in all organisms consist primarily of hydrolysis 

 and only secondarily of oxidation cannot be definitely decided 

 at present, but it seems very probable that in many of the 



1 Vernon, Jonrn. Physiol. 39, p. 149, 1909; 40, p. 295, 1910. 



