PRESIDENTIAL ADDRESS. 121 
sunlight, decompose the carbon dioxide of the. air, build the 
carbon and the elements of water into their structure, and 
liberate the oxygen. This justified the at once apt and 
poetical description of plants, as “the air-woven children of 
light.” This work is being reviewed, and the investigations 
extended, by Dr. Horace T. Brown, who has already thrown 
much interesting light upon many phases of this question. 
The plant respiration appears to take place through the 
stomata rather than by osmosis, and some of the carbon seems 
to be derived from the soil. . 
Very great. attention has been directed of late years te 
the question of the fixation of the nitrogen of the air, and 
recent investigation is bringing us nearer the solution—the 
economic preparation of nitrogenous plant food from the 
nitrogen of the air. We should then have a virtually un 
limited supply of nitrogenous plant food to replenish the 
enormous impoverishment of the soil by the growth of wheat 
and similar foodstuffs. 
RELATION TO ANIMAL LIFE. 
The effect of the animal upon the air had also been clearly 
demonstrated, and the study of this question branched out 
into long series of investigations of the utmost importance, 
both to the individual and to the community. Quantitative 
determinations had to be made of the rate of combustion of 
the human body, expressed in terms of carbon; the amount 
of impttrity communicated to the air by each individual, 
from which the amount of air required per individual could 
be calculated. It opens upon the important subject of ven- 
talation—of the home, of public buildings, of the school, the 
factory, the church, the mine. The science of ventilation is 
charged with the supply of fresh air without draught, or 
without’ undue draught, and is expected to devise means for 
meeting this demand. It is daily forced upon our attention 
that this is a problem of the utmost difficulty still awaiting 
a satisfactory solution. _ In principle so easy, in practice so 
seemingly beyond our reach. But it is a problem that is 
always with us, and one that can and must be solved, and . 
its practice must be controlled and enforced by legislation. 
One of the first cares of every government should be to see 
that the people are supplied with fresh air, pure water, and 
wholesome food. Fortunately for the future of our race, 
the whole world is alive to this to-day. 
