1885. J 
Recent Researches in Malaria. 665 
Those sanitations which are aimed at by laying malarial 
districts bare of trees are of a purely hydraulic nature. 
'Surely some of the most malarial districts of the world — 
such as the neighbourhood of Rome, many parts of India, 
Peru, &c. are distinguished by the absence of woods.] 
Whilst we formerly spoke of the action of woods in puri- 
fying the air and filtering out the malaria, the conviction 
gains ground that, as the destruction of the woods removes 
a hindrance to the direCt aCtion of the solar rays upon the 
soil, to remove all moisture during the hot season in districts 
with a shallow soil would improve their salubrity. [The 
desiccation of the subsoil by the aCtion of the sun’s rays 
upon the surface is an exceedingly slow process. Trees 
which send their roots down to the lower strata, and suck 
up large quantities of moisture, are more effectual than the 
direCt aCtion of the sun on the surface.] 
i( So long as the nature of malaria was sought for in the 
miasmatic, putrid exhalations of the swamps,” this view 
of the protective aCtion of forests had a similar meaning to 
the plantations of Eucalyptus, whose powerful aroma was 
to destioy the poisonous exhalations. But favourable as is 
the aCtion of rapidly growing plants in promoting the drain- 
age of the soil, the experiments with the Eucalyptus in 
Pola and Italy were not satisfactory. The trees are very 
sensitive, and easily suffer from frost. [This, of course, 
does not apply to climates warmer than Italy.] They are 
often damaged by the wind, and they are costly. A specific 
aCtion can scarcely be admitted, since there are in Australia 
entire forests of Eucalyptus in districts where malaria is 
endemic. [Without admitting half of what has been said 
concerning the efficacy of the Eucalyptus, w'e may still ask 
Why should Australia, in a lower latitude than Italy, 
suffer so much less from malaria ?] It cannnot be valued 
more highly than other water-absorbing plants, such as the 
sunflower. 
2 Y 
VOL. VII. (THIRD SERIES.) 
