340 Htalian Malaria. 
abundance in different parts of Italy and Sicily which are neverthe- 
less considered as very healthy. 
The effect has also been imputed to exhalations of azotic gas ; but 
this gas being lighter than atmospheric air would necessarily rise and 
thus render the heights more unhealthy than the vallies, while sxe 
ee ieee that the contrary is the fact.* 
he Campagna of Rome is an extended country, cut up by little 
a and mostly in an uncultivated state. During the rainy season, 
the water collects in the vallies and forms pools where it stagnates, 
and having brought with it all sorts of vegetable substances as well 
as animal refuse, it becomes corrupted. At the return of the warm 
season which augments the putrefaction, these ponds and marshes 
send forth their vapor, but as the process of evaporation g goes on 
slowly, the heat being still moderate, the atmosphere is not much 
changed until the month of July brings with it a greatly increased 
temperature, which accelerates the evaporation, and which is accom- 
panied by fevers a duration equals its own ; that is to say, it is 
prolonged to Septem 
If the Campagna were ener where properly cultivated, as it was 
formerly, the air would not be subject to this alteration; for the rains 
of winter would not then collect as they do in the low grounds, but 
would be absorbed by a mellowed soil, and evaporated by the influ- 
ence of the heat. 
It must not be urged against this opinion, that in Lombardy, espe- 
cially in the plains which extend from Bologna to Ferrara, the vast 
fields of Rice are, during the whole winter, covered with water, and 
that the country is nevertheless not unhealthy, or at least not so much 
so as that of Rome. These artificial lakes or inundations, as I have 
myself observed, are first, on account of their extent, always agitated 
by the wind, like a lake of water, and also by the action of the sluices 
by which they are supplied and drained, the current of water is con- 
tinually entering and passing from them. These two causes com- 
bined prevent putrefaction. 
le we admit, with the author that azotic gas is not the probable cause of 
epidemic vieodlyee we must object to the soundness of his Soo with respect to 
ere sie —_—— easton _ than atmospheric air, it is, we believe 
hemistry, to one ‘that the ace of 
any pital if set fee | ae the atmosphere, wil I (oltimataly) arrange themse ee 
have no in 
mer fr or do not combine with With constituents of the air. Such is the Daltonian theory, 
