1922.] Indian Science Congress. 1.8 C. 167 
portance attaches to the study of meteorological conditions in relation 
to the transmission of malaria and indeed of all insect-borne diseases. 
They afford also a scientific basis for the hypothesis of Galen (to 
whom malaria was well known) that ‘‘ the seeds of pestilence,” which a 
regarded as floating in the air, re (iis for their propagation ‘‘ a war 
and moist state of the atmosphere 
(3).. The Role of Climatic shdervsioted in the Mechanism of Epidemic 
falaria. 
When the meteorological circumstances necessary for the transmis- 
sion of malaria are considered in the light of the climatic conditions pre- 
vailing i in the Punjab some AB facts “ rge. 
It is found, at the result of a study of t ape gece and humidity 
ata pars in the viene gical Re be om that the transmission a 
aa isin abeyance during the cold weather on pat of low tem 
ure, 
uring the spring there is normally a short period during which 
both pcre and humidity - Jabot ble to infection. With the 
rise in me mpera ature which ushers in the hot weather the transmis- 
— of inthiont is again Reiss: at to low mean relative humi- 
ity. 
ith the onset of the piso a marked rise in relative humidity 
take s place and both the t mperature and humidity factors become fa- 
vatecble t the eraiaeaaii of infection 
av avhige years the annual period ot potential —— is hor to 
be approximately 4 months in most parts of the plains, but in 
deficie ns oe rain’ a8 - is much pi as it is ewig: 
ring “ bre n the con. On the other hand in years of exces- 
sive rainfall he setueusenieaeal factors remain highly favourable to the 
ransmission of infection throughout the monsoon period 
t is in these latter years alone that great epidemics of m alaria occur 
j the 
or do t cur in areas where the rainfall is relatively or absolutel 
in excess. - is in fact found that malaria epidemics are strict on- 
fined to a exhibiting climatic conditions which, whilst jaar! dg 
area 
tively unfav ater to the transmission of infection, become highly 
vourable to infection and re-infection on rare occasions. 
vation “etouiil te the fact that great 
This epidemiological obse 
epidemics saa m alaria are not encountered in all malarious countries _ 
are only ith in areas exhibiting climatic conditions similar to those 
= ope see of the plains of the Punjab. 
imatic Sanne therefore cons es an exceedingly important 
actor 4 e cage of m 
Cli i ares ee ec cae ee the gecurrence 0 of ihese epidemics 
during the period immediately following the rainy se 
seasonal periodicity of malaria epidemics is es a 1 function of the 
The 
li 
clisnatic  fator mperature and humidity in re the 
aie assigned t 
: e well-known associa n of ex nd 
transmission of malaria aia that th eos bxplain pag ng due 
sive photic with epidemic malaria may ie a ailciy 0) rather than te 
osqui sep 
* ee : . al pre- 
Finally, it is clear that, since excessive rainfall is an essen 
cursor of af epidemic of aes ria, this climatic factor constitutes ms direct 
and immediate ca : 
ese Gulcleckane a ~ well-fonnded, suffice to show pide ope 
— et intimately the mechanism ans ai ct 
They are also not sey: Coors ciporneiios e from the ney 
Thus ey is now possible with the aid of meteorological 
