6o8 PRINCIPLES OF GENERAL PHYSIOLOGY 



than carbohydrate is oxidised. Now, supposing that, while in oxygen, the 

 preparation has accumulated to itself a store of oxygen in disposable form, as 

 " biogens " or otherwise, then, when nitrogen takes the place of oxygen, this store 

 of oxygen will be used up. Therefore, the first thing that will happen, when the 

 nitrogen is again replaced by oxygen, will be that the store is replenished 

 and oxygen will disappear without the corresponding amount of carbon dioxide 

 being given off; in other words, the respiratory quotient will not be the 

 same as that after being some time in oxygen. In very carefully controlled 

 experiments no indication was found of any change of this kind. 



It appears, then, that, although inexcitable, the tissue remains alive in 

 nitrogen, since its excitability can be restored in oxygen. Since the survival 

 is not an 'oxidative process, why is oxygen necessary for restoration of ex- 

 citability 1 Winterstein compares it to a clock which has stopped, not because 

 the spring has run down, but because the movement of the pendulum is 

 hindered. In our case the hindrance is the accumulation of asphyxial pro- 

 ducts, which require oxygen to remove them. The length of time necessary 

 for recovery is not due to slowness of diffusion of oxygen, but to the rate 

 of oxidation of these products. Whatever they may be, it seems clear from 

 the non-alteration of the respiratory quotient that their chemical nature is 

 similar to that of those oxidised under normal conditions. It is scarcely 

 necessary to remark that, after asphyxia, the rate of consumption of oxygen 

 was temporarily increased, but the point is that the respiratory quotient was 

 unaltered, as it would have been if oxygen were being stored apart from 

 simultaneous production of carbon dioxide. 



In the researches of Battelli and Stern (1907), however they may be 

 interpreted, there is no evidence of storage of oxygen. 



Meyerhof (1912, 1, p. 176), again, finds that in the absence of oxygen, 

 there is no production of heat in the blood corpuscles of the goose, although 

 it returns on admission of oxygen. 



Thunberg (1905, 3), in some experiments to be referred to again later, 

 found that the oxygen consumption of the slug and the earthworm was 

 increased by increase of oxygen pressure, but that the carbon dioxide pro- 

 duction was always parallel to it, so that no storage of oxygen took place, 

 even under increased pressure. 



The experiments of Falloise (1901) and of Durig (1903) are regarded by 

 Zuntz as affording definite proof of the absence of any kind of storage of 

 oxygen on the part of the cell. 



Falloise showed that, if an animal were caused to breathe for a considera hit- 

 time a mixture rich in oxygen, and then the supply cut off, symptoms of 

 asphyxia appeared only forty-five seconds later than they did if ordinary air had 

 been breathed. If the oxygen inhalation only lasted for one minute, the 

 same effect resulted, and, if air were breathed for one minute after the oxygen 

 inhalation, its effect was removed. Hence the only effect produced is that 

 of the residual air in the lungs and the extra oxygen dissolved in the plasma. 



Durig's experiments were made in Zuntz' laboratory by the most accurate 

 methods and they resulted in confirming the work of Falloise. Dogs were 

 given mixtures of air with various percentages of oxygen, and the intake per 

 minute was determined. During the first two to three minutes after changing 

 the mixture, the oxygen intake was increased or decreased in proportion to 

 the oxygen content of the air breathed. Special experiments were then made 

 to determine the amount present in the air of the lungs and that dissolved 

 in the tissues and blood. It was found that the whole of that taken in or 

 given out beyond the normal amount was required for these purposes, so that 

 none at all was left over for storage in any other form. 



We saw above (page 343) that the results of the experiments of Barcroft and 

 Brodie (1905, p. 65) are opposed to the view of intra-molecular oxygen in 

 this case. 



Those of Evans and Ogawa (1914) are also of interest in this connection, 

 as well as with regard to the mechanism of tissue respiration. They found that 



