156 TEEES AS A PKOTECTION AGAI]S"ST MALARIA. 



in Italy, and there is some reason to think that under special cir- 

 cumstances the influence of the forest in tliis respect may be 

 prejudicial rather than salutary, though this does not appear to 

 be generally the case.* It is, at aU events, well known that the 



* Salvagnoli, Memorie sulle Maremme Toscane, pp. 313, 214. The sanitary 

 action of the forest has been lately matter of much attention in Italy. See 

 Bendiconti del Congresso Medico del 1869 a Firenze, and especially the import- 

 ant observations of Selmi, 11 Miasma Palustre, Padua, 1870, pp. 109 et seq. 

 This action is held by this able writer to be almost wholly chemical, and he 

 earnestly recommends the plantation of groves, at least of belts of trees, as 

 an effectual protection against the miasmatic influence of marshes. Very in- 

 teresting observations on this point will be found in Ebermayer, Die Physik- 

 alischen Einwirkungen des Waldes, Aschaffeuburg, 1873, B. I., pp. 237 et seq., 

 where great importance is ascribed to the development of ozone by the chemi- 

 cal action of the forest. The beneficial influence of the ozone of the forest 

 atmosphere on the human system is, however, questioned by some observers. 

 See also the able memoir : Del Miasma vegetale e delle Malattie Miasmatiche of 

 Dr. D. PantaIiEONI in Lo SperimentaU, vol. xxii., 1870. 



The necessity of such hygienic improvements as shall render the new capital 

 of Italy a salubrious residence gives great present importance to this question, 

 and it is much to be hoped that the Agro Romano, as well as more distant 

 parts of the Campagna, will soon be dotted with groves and traversed by files 

 of rapidly growing trees. Many forest trees grow with great luxuriance iu 

 Italy, and a moderate expense in plantation would in a very few years deter- 

 mine whether any amelioration of the sanitary condition of Rome can be ex- 

 pected from this measure. 



It is said by recent writers that in India the villages of the natives and the 

 encampments of European troops, situated in the midst or in the neighbor- 

 hood of groves and of forests, are exempt from cholera. Similar observations 

 were also made in 1854 in Germany when this terrible disease was raging 

 there. It is hence inferred that forests prevent the spreading of this malady, 

 or rather the development of those unknown influences of which cholera is 

 the result. These influences, if we may believe certain able writers on medical 

 subjects, are telluric rather than meteoric ; and they regard it as probable that 

 the imiform moisture of soU in forests may be the immediate cause of the im- 

 munity enjoyed by such localities. See an article by Pettenkofer in the 

 Sad-Deutsche Presse, August, 1869 ; and the observations of Eberjiater in 

 the work above quoted, pp. 246 et seq. 



In Australia and New Zealand, as well as generally in the Southern Hemi- 

 sphere, the indigenous trees are all evergreens, and even deciduous trees intro- 

 duced from the other side of the equator become evergreen. In those regions, 

 even in the most swampy localities, malarious diseases are nearly, if not alto- 

 gether, unknown. Is this most important fact due to the persistence of th« 

 foliage ? 



Mobsman, Ongin of Climates, pp. 374, 393, 410, 425 et seq. 



