GLEANINGS 
IN 
SCIENCE. 
JYo. 3— March, 1829 . 
I . — On Malaria. By J. Macculloch, M. D., F. R. S., &c. 
[From the Journal of Science, N. S. Vol. II.] 
It is a familiar fact, not merely to physicianshut to the people at large, that there 
is produced from marshy lands a peculiar substance, called, marsh miasma, in phy- 
sic, and to which Italy has given the term Malaria ; from the effect of which on 
the human body, there are excited fevers of different characters, but generally 
divided under the two great leading heads of intermittent and remittent. What 
the chemical nature of this substance is, has not been discovered, though numerous 
experiments have been instituted for this purpose; yet with respect to its proper- 
ties, we know enough to believe that it is a compound gas, decomposable by certain 
agencies, and also capable of being conducted to certain distances from the place 
of its production, by the winds. Further, it is ascertained, that it can be condensed 
or accumulated in particular places ; that it can form a certain attachment to the 
soil, or to peculiar solid bodies, although this is not permanent, as happens with 
respect to the matter of contagions ; and lastly, that it is particularly affected, both 
in respect to its propagation and production, by certain qualities of the atmosphere, 
consisting in its conditions as to temperature and hygrmnetrical moisture. 
Thus, although ignorant of its nature, we are in possession of certain facts ap- 
pertaining to its natural history, which we can convert to use in warding off its 
evil influences, or preventing the attacks of the diseases which it produces ; while, 
if one class of precautions depend on this knowledge, the other consists in that re- 
maining branch of its natural history, which relates to the causes through which 
it is, in the first instance, produced, and in the next., propagated. 
Being, as I have remarked, produced by marshy lands very especially, it has been 
naturally concluded that its immediate cause was the mutual action of vegetables and 
water, though it has l>een disputed in what that precise action consisted. To 
ascertain this is, however, of some importance, as on the nature of that action must, 
in a great measure, depend under what particular circumstances it is produced ; 
consequently, what places ought to be suspected, and, in the view to prevention, 
avoided. 
That it is the produce of vegetable decomposition cannot, apparently, be ques- 
tioned ; because, if it were extricated from living plants, it should be found in 
thousands of situations where it is unknown ; and that it belongs to wet soils, and 
also to hot countries, or to a high temperature, further proves that it depends on 
that process of decomposition which notedly occurs, in these circumstances, most 
rapidly ami extensively. Hut a difficulty remains in attempting to determine what 
is the peculiar quality or stage of this decomposition under which it is produced • 
whether it is the process commonly called putrefaction, or some change among the 
elements of plants of a different nature. 
One point is at least provided ; viz. that it is not necessarily accompanied by 
any smell, or that it is not an odorous substance in itself. It may exist in abund- 
ance and virulence, without being sensible in this manner ; and hence it had been 
thought this arose from some mutual action of vegetables and water, which was in- 
dependent of proper decomposition. This, however, must be an incorrect opinion ; 
or the living vegetable is not required for its production : since it is fully proved to 
