8o RESPIRATION 



is sufficiently large to effect a visible disorganization, such as 

 change in colour,* there is an initial outburst of carbon dioxide 

 then a fall to a very low level and the absorption of oxygen 

 no longer shows any co-ordination with the amount of carbon 

 dioxide evolved. The absorption of oxygen in some way is 

 connected with the cell contents, especially tannin. In the 

 Tropceolum leaf, which is free from tannin, the absorption of 

 oxygen is much lower than the output of carbon dioxide, where- 

 as in the cherry laurel and the artichoke, both of which contain 

 tannin, the initial up-take of oxygen is very rapid, then it 

 declines but remains at a level much higher than the output 

 of carbon dioxide. 



Similar observations have been made by others, thus 

 Thomas f found that wheat subjected to the action of ether 

 shows an increase of respiration followed by a decrease. 

 Exposure to 7-3 per cent of ether is only stimulatory provided 

 it be of short duration, an exposure of more than thirty 

 minutes resulting in death. Similarly the main observations 

 of Thomas have been corroborated and extended by Smith J 

 who used the hydrogen ion concentration method in finding 

 the rate of production of carbon dioxide in wheat seedlings. 

 It was found that the first effect of ether, used in concentrations 

 of I per cent, 3*65 per cent and 7*3 per cent, was to depress 

 the rate of respiration ; this was followed by a rapid increase 

 to above the normal rate, which was in turn followed by a 

 decline to much the same level in all concentrations of anaes- 

 thetic in times varying with the dose employed ; the stronger 

 the solution of ether used, the quicker the fall. 



Irwin found in the instance of the corolla of Salvia that 

 the effect of a high concentration of ether is an increased intake 

 of oxygen and output of carbon dioxide whilst at the same 

 time the acidity of the cell sap is reduced. With regard to the 

 lower plants, the action of anaesthetics results in reactions similar 

 to those exhibited by higher plants under like treatment 



* The change in colour is due to the oxidation of tannins and glucosides by 

 appropriate enzymes, oxidases for example (see Vol. I., p. 392). It may be 

 conveniently seen by exposing the flowers of the white lilac to the fumes of 

 phenol under a bell glass. 



i Thomas: " Journ. Gen. Physiol.," 1918, I, 203. 



Smith : Id., 1921, 4, 157. Irwin : Id., 1909, I, 399, 



