PREVENTION AND PRODUCTION OF MALARIA. 601 
be caused by the decomposition of organized bodies. If so, 
it must exist to some extent everywhere. By the mode 
of testing the air invented by the author, every place 
tried at home and abroad was found to have some oxidiz- 
able matter in it, although in some this was extremely 
small. In such cases the matter was probably oxidized to a 
state in which it would be innocuous. This oxidizable 
matter no doubt arises, in a great measure, from vegetation. 
Vegetation does not merely grow; it dies. This death may 
be caused by various circumstances, but two conditions are 
remarkable, one where the agents are animals, and the other 
where the agents are chemical. Animal life may act in 
various amounts on vegetation in the soil, from the large 
vermin to the microscopic classes. These do not prevent 
chemical action; on the contrary, it is probable that they 
further it exceedingly. Decomposition goes on in the soil at 
various rates, and in various ways. In a rich, highly manured 
soil, kept warm, the soil will be found alkaline. Soils gene¬ 
rally are acid. The author has shown in a paper, read in 
1847, that in an alkaline, peaty district, cold weather produced 
acidity in a few days. It would appear as if the acids of the 
mould (so elaborately described by Mulder) were incapable 
of further decomposition in the cold, and where thus retained 
and increased. Our great struggle with the soil is to produce 
alkalinity, or at least to diminish acidity, and where most acids 
exist we use most lime. Where most alkali exists there is a 
greater facility for the escape of vapours such as we suppose 
to be hurtful. So far as the vapours of putrid substances 
have been examined by the author, they have shown indica¬ 
tions of containing substances composed somewhat like 
protein, at least the carbon and nitrogen have had relations 
to each other similar, or nearly identical with those found in 
protein, and formed the mass of the substance. 
“ The extreme condition of putrescence may be very readily 
produced in a soil by artificial means; the use of a little 
ammonia, for example, more than vegetation will bear. The 
substances putrefy until the whole becomes fetid in the 
highest degree. We have then a soil rich in organic matter 
and undrained. It is a swamp of the worst form, if the soil 
be not very poor; worse, perhaps, than was ever seen in 
nature. Such a soil would bring death everywhere. It is 
artificial malaria. We can, then, produce malaria from the 
soil by fostering some of its tendencies ; and we see by the 
rapid acidification of the soil, in colder weather, why malaria 
is diminished by a lower temperature. 
“As we can imitate malaria of some kinds, so can we also 
