II A RT V UNTIL AT I ON 
33 
of Carbon dioxide and other elements contained in a en al1 
space, showing that numerous cubic feet of air arc necessary to 
pass in currents over the surface of the leaves to allow of the 
Carbon dioxide being abstracted, for use in their internal 
economy. 
Ventilation is also necessary to remove any noxious gases 
that may arise from decomposing or heated material inside the 
structure or from any accumulations of vitiated air generated b) 
the heating apparatus or other causes. I have seen nitrogen in 
the form of ammonia completely destroy the young leaves of the 
£ ra pe vine in a single night, and where fermenting material is 
u ^ed for any purpose, it is essentially necessary that the system 
°f ventilation should be sufficient to remove any of these gases 
which may arise in. excess of the actual requirements of cultiva- 
tion for although nitrogen in excess is pernicious, it is known to the 
cultivator that the presence of free ammonia in suitable quan- 
tities tends greatly to the healthy development of plants, and in 
Horticultural structures is freely applied in an artificial manner. 
To sum up, ventilation is necessary to preserve the health of 
plants, to assist their growth, to avert any danger which may 
ar * se through the absorption of noxious gases, and to maintain 
an equable temperature suited generally to their development. 
In the same way that ventilation is necessary to plant life, 
80 a lso is it necessary to human or animal life and for the exactly 
the same reasons (viz.) to preserve the health, to supply the gases 
111 due proportion necessary to the existence of life— to avert 
danger through the inhalation of noxious gases, and to maintain 
ari equable temperature suitable for the comfort of the body. 
Thus it is seen that ventilation is as necessary to plants as 
to animals, the gases which are necessary to plants are those 
expired by animals, and the gases given olf by plants are necessary 
to animals, the animal being dependent on the vegetable and the 
vegetable being dependent on the animal, together with the 
mineral kingdom, for its supplies. 
