I885J 
Recent Researches on Malaria. 
661 
VI. THE RESULTS OF RECENT RESEARCHES 
ON MALARIA* 
By Dr. Hans Schceffer. 
t LL experience and observation hitherto made on the 
nature of malarial diseases points very decisively to 
the fadft that its true cause must be sought in the soil 
of those localities in which such diseases are prevalent. 
If we search for the factors and the circumstances which 
favour the development of the supposed exciter of the ma- 
larial process, we are struck by the accordant statement 
that malarial disease occurs endemicallv, especially where 
the physical condition of the soil or that of the subsoil pre- 
vents a rapid efflux of the water. 
Such conditions prevail most decidedly in swamps. Here 
accordingly it is found that malaria prevails most intensely 
when, in the dry season, the ground is covered only with a 
shallow layer of water, and is here and there laid bare. As 
long as the swampy ground is entirely under water the 
generation of malaria is trifling or altogether wanting. 
Hence we do not find malaria in all swampy regions. In 
hot climates especially there are extensive swamps where it 
is pradlically absent. 
[As an affirmative instance may here be mentioned the 
Dismal Swamp of North Carolina, where “ fever and chills ” 
are less prevalent than in the fairly dry cultivated lands of 
the same State.] 
On the other hand, malaria is encountered not merely in 
swamps, but also in well-watered valleys exposed to frequent 
inundations, where, in consequence of their position, the 
waters cannot drain rapidly away. Such conditions are 
found in clays and alluvial soils, which always contain a 
sufficiency of water, at least in their lower strata. 
Under other circumstances malaria occurs, even on appa- 
rently very dry ground, when beneath the porous surface-soil 
there lies an impervious subsoil. Thus foci of malaria may 
occur in elevated districts, and even in mountain chains. 
Thus they exist in the Apennines of Tuscany at the height 
of i ioo feet, in the Pyrennees at 5000, and in Peru up to 
10,000 to 11,000 feet. In Italy especially, according to an 
* A Discourse delivered before the Vienna College of Physicians. 
