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VOLUME XXXIX NUMBER 2 
BOTANICAL, GAZETTE 
FEBRUARY, 1905 
THE THEORY OF RESPIRATION.° 
CHARLES R. BARNES. 
I Ask you to consider with me a topic which is of fundamental 
interest to physiologists, whether they concern themselves primarily 
with animals or with plants. I take it the basal identity of the living 
matter in all organisms and of its metabolism needs neither demon- 
stration nor emphasis at my hands. Nor do I need to lay stress 
upon the importance of respiration as one of these metabolic phe- 
nomena, since it has been recognized from the earliest period as 
indispensable to life. The phlogiston theory of the composition of 
the atmosphere had scarcely disappeared below the scientific horizon, 
before the fact was discovered that there occur, in animals and in 
plants alike, an intake of oxygen and an output of carbon dioxid 
which are intimately related to their existence. This became obvi- 
ous to man, of course, in his own experience, a very superficial study 
of the composition of the air inspired and expired from the lungs 
showing that it had lost oxygen and gained CO,. This much of 
Tespiration was early recognized to occur also with the larger ani- 
mals, and a few years later like observations were made upon plants 
by Prrestiey, and more accurately by LAVoIsIER and INGENHOUssS. 
Even this knowledge of respiration was not possible before PRrest- 
LEY’S discovery of oxygen in 1774, and the very remarkable revo- 
lution in chemistry that followed in the closing years of the eigh- 
teenth century. Yet this disappearance of oxygen and formation 
of carbon dioxid are only the external indication of respiration, as 
has on aie recognized. 
of the retiring president before the Botanical Society of America, Phila- 
detphia Seite: December 28, 1904. Published also in Science. 
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