December.'] ROOMS — CAMELLIAS. 305 
and give out oxygen by their under ones, thereby tending to 
purify the air, in as far as animal life is concerned, because 
carbonic acid gas is pernicious to animals, and oxygen is 
what that life requires. It is in the light, however, that 
these operations are carried on, for in the dark, plants give 
out carbonic. It does not appear that any of the scentless 
products given out by plants are injurious to human beings, 
because those who live among accumulated plants are not 
less healthy than others, but rather enjoy more uninterrupted 
health, which, of itself, is a sufficient recommendation for 
all to spend their leisure moments in so healthful and rational 
an employment. 
