ADDRESS. 25 



-with the seeds which were the object of the experiment a solution of 

 barytes, when the carbonate became precipitated from the solution in 

 quantity equal to that produced in a similar experiment with seeds ger- 

 minating in unetherised air. 



So, also, in the experiment which proves that the faculty possessed by 

 the chlorophyllian cells of absorbing carbonic acid and exhaling oxygen 

 under the influence of light may be arrested by anaesthetics, it could be 

 seen that the plant, while in a state of anaesthesia, continued to respire in 

 the manner of animals : that is, it continued to absorb oxygen and exhale 

 carbonic acid. This is the true respiratory function which was previously 

 masked by the predominant function of assimilation, which devolves on 

 the green cells of plants, and which manifests itself under the influence 

 of light in the absorption of carbonic acid and the exhalation of oxygen. 



It must not, however, be supposed that the respiration of plants is 

 entirely independent of life. The conditions which bring the oxygen of 

 the air and the combustible matter of the respiring plant into such rela- 

 tions as may allow them to act on one another are still under its control, 

 and we must conclude that in Claude Bernard's experiment the anaes- 

 thesia had not been carried so far as to arrest such properties of the 

 living tissues as are needed for this. 



The quite recent researches of Schiitzenberger, who has investigated 

 the process of respiration as it takes place in the cell of the yeast fungus, 

 have shown that vitality is a factor in this process. He has shown that 

 fresh yeast, placed in water, breathes like an aquatic animal, disengaging 

 carbonic acid, and causing the oxygen contained in the water to dis- 

 appear. That this phenomenon is a function of the living cell is proved 

 by the fact that, if the yeast be first heated to 60° C. and then placed 

 in the oxygenated water, the quantity of oxygen in the water remains 

 unchanged ; in other words, the yeast ceases to breathe. 



Schiitzenberger has further shown that light exerts no influence on 

 the respiration of the yeast cell — that the absorption of oxygen by the 

 cell takes place in the dark exactly as in sunlight. On the other hand, 

 the influence of temperature is well marked. Respiration is almost 

 entirely arrested at temperatures below 10° C, it reaches its maximum at 

 about 40° C, while at 60° C. it again ceases. 



All this proves that the respiration of living beings is identical, 

 whether manifested in the plant or in the animal. It is essentially a 

 destructive phenomenon — as much so as the burning of a piece of 

 charcoal in the open air, and, like it, is characterised by the disappear- 

 ance of oxygen and the formation of carbonic acid. 



One of the most valuable results of the recent careful application of 

 the experimental method of research to the life phenomena of plants 

 is thus the complete demolition of the supposed antagonism between 

 respiration in plants and that in animals. 



I have thus endeavoured to give you in a few broad outlines a sketch 



