Dec. 2, 1901.J Su^tement to the " Tropical AgricitUurist." 
439 
nutrition is supplied to the plant as well as the 
elements and sources of plant nutrition are yery 
different from those of animal natririon. All 
animals, including human beings, are either 
carnivorous, herbivorous or both, that is to say, 
they consume animal food or vegetable food or 
subsist on a mixed diet. But vegetation is the 
ultimate source of all animal food, for either 
directly or indirectly it is to the plant that 
we must trace the source of animal nutrition. 
We can imagine, for the sake of argument, 
a man becoming independent of animal food, iu 
the absence of animal life, but we cannot imagine 
the opposite state of affairs, for granted that 
human beings can maintain themselves on a 
purely meat diet, the latter would not be 
available inasmuch as vegetation would still be 
necessary for the nutrition of the lower animals 
whose flesh we consume. It comes to this then, 
that plant life is absolutely necessary for 
human nutrition. 
Let us now enquire how plants get their food. 
The source of plant food are the atmosphere 
and the soil. From the atmosphere the plant 
draws one very important element of plant food, 
namely, the carbon which helps to build up 
the framework of the plant. 1 have already been 
speaking to you about tlie carbonic acid which 
is present in the atmosphere. It may be said 
to be an adulterant in an otherwise pure 
atmosphere consisting of nitrogen and oxygen, 
and is produced as the result of respiration 
(exspiration) of all animals and plants, as well 
as of the combustion and decomposition of organic 
substances. As a result the oxygen of the 
atmosphere has a great tendency to be exhausted 
and to be replaced by carbonic acid, for it is 
the oxygen of the atmosphere that combiues 
with carbon from whatever source to form car- 
bonic acid. But the composition of the atmo- 
sphere, as I have already told you, is practically 
constant in spite of tliis, that is tlia proporUons 
of nitrogen and oxygen vary very slightly, at 
any rate not to a sufficient extent to cause any 
inconvenience to human beings. Under normal 
conditions there are to every 100 parts of 
atmospheric acid, 79 of nitrogen and '21 of oxygen, 
and this quantity of pure air is ordinarily adulter- 
ated with l-25th part of carbonic acid. 
Now the means by which the composition of 
the air remains practically unchanged is the 
same means by which plants obtain carbon from 
the atmosphere. This process is technically 
known as assimilation, and consists of carbonic 
acid being taken by the plant from the air through 
the stomata, the carbon retained or fixed, 
and the oxygen given out. It is like a sum in 
subtraction ; the plant takes iu carbon and oxygen 
in combination as carbonic acid, substracts the 
carbon and liberates the remaining oxygen. Now 
you will see how the plant purifies the atmo- 
sphera while it secures the carbon necessary for 
its nutrition. This process is, indeed, the exact 
opposite of the process of respiration, which 
consists of the taking iu of oxygen and the 
giving out of carbonic acid. There is no difference 
in the process of respiration as carried on by 
plants and animals ; but assimilation in plants 
is the opposii-e process which counteracts the 
effecis (rhe vitiaiiug of t,he atmospiieie by 
accu;nulation of carbonic acid), of respiration 
in plints and animals, and not only re.^pirariou 
but also the combustion iiiid d^compuoidun of 
orgu! ic matter. Thus is the a mo.-phere pre- 
served iu a condition suitable for human hfe. 
GENERAL ITEMS. 
According to an American paper the Public 
Health Journal), the dreaded mosquito, which is 
such an intolerable nuisance in the summer 
months, more particularly along viver banks and 
on the sea coast, can be easily abated by the use 
of a very simple remedy, It is stated that but 
two and a-half hours are required for the develop- 
ment of the full-grown mosquito from a mere 
speck, its first stage. It can be instantly killed 
either in its infancy or at maturity by contact 
with minute quantities of permangu.uate of potash, 
the cheap purple salt which is used so much for 
di.^infecting purposes. It is said that a solution 
of the salt containing only one part in fifteeu 
thousand of water, distributed in the marshes 
where the mosquito breeds, will render the deve 
L pment of their larvee impossible. To quote the 
Journal itself : — "A handful of permanganate will 
oxidise a ten-acre swamp, kill its embryo insects, 
and keep it free from organic matter for thirty 
days at a cost of 2-5 cents. With care, a whole 
State may be kept free of insect pests at a small 
cost. An efficacious method is to scatter a few 
crystals widely apart. A single pinch of perman- 
ganate has killed all the germs iu a 1,000-gallou 
tank,'' 
Not many people are aware that the onion con- 
tains a principle which acts on tiie nerves in a 
manner similar to the action of opium. Unfor- 
tunately, the persistent odour of the vegetable 
makes sensitive persons disinclined to use them 
at all events in the raw state. Now, an onion 
taken at night is one of the best sleepinducers. 
Tlie element above mentioned has the effect of 
calming the nerves, and consequently of lulling 
the brain to rest. 
A correspondent to the Queensland Agricultural 
Journal, writing of the Brinjal as a neglected 
vegetable, says : "It is a vegetable of considerable 
excellence and has the merit of being Imrdy and 
very easily cultivated. Care should be taken to 
gather the brinjal before it passes its prime ; 
otherwise it is unpalatable. The purple-fruited, 
of which there are seA'eral variei ies, is usually 
cultivated for the table; it sho.ild be picked 
before it loses its brilliant purp e hue. There 
are several ways of cooking it ; an approved way 
is first to boil it from '20 to 30 minutes, then to 
slice and fry it. When thus treated, it is a 
delicious vegetable. I noticed when in London 
and Paris, last season, that the brinjal was 
frequently in evidence. The price quoted was 
about 2rf, or Zd, each, It is known in London by 
