146 
MALARIA 
by James and Christophers (1922) and Gill 
(1938a). The former authors recognize 
temperate, sub-tropical and tropical zones, 
and the latter divides the distribution of 
malaria into 4 zones as follows: 
Zone 
Meteorological 
characteristics 
Type- 
area 
Tem¬ 
perate 
Temp. 16-20° C dur¬ 
ing hot-test months. 
E. H. 70 per cent or 
more. 
Holland 
Sub¬ 
tropical 
Temp. 20-25° C. E. 
H. 50 per cent or 
more. 
S. Italy 
Tropical 
Temp. 25° C or more. 
E. H. 50 per cent or 
less. 
N. India 
Equa¬ 
Temp. 25° C. E. H. 
Ceylon 
torial 
70 per cent or less. 
(Wet Zone) 
Different epidemiological types of malaria 
exist in each of the roughly-defined endemic 
belts, and elsewhere in this monograph 
these types are described. 
According to Gill’s classification there 
are seven climatic zones of malaria in the 
two hemispheres. A single type of malaria 
is not universally distributed throughout 
each zone, however, since local topograph¬ 
ical features (high altitudes in particular) 
may inhibit mosquito breeding. Further¬ 
more, the presence of large bodies of water 
or deep mountain-rimmed valleys may af¬ 
fect the temperature and humidity of sur¬ 
rounding regions, and either favor or deter 
mosquito propagation. 
Rainfall is another factor which is greatly 
affected by regional topography. Arid or 
semi-arid regions such as occur in the south¬ 
western states and northern Mexico are the 
direct result of the Rocky Mountain and 
Pacific Coast ranges. In the western United 
States the atmospheric drift from the Pa¬ 
cific Ocean gives part of California, Wash¬ 
ington and Oregon a marine climate, with 
small annual or diurnal temperature 
changes. In California most of the rain¬ 
fall occurs in the winter months. The west¬ 
ern mountain ranges, however, precipitate 
most of the moisture brought from the Pa¬ 
cific on their windward slopes, making the 
great region between the 120th and 100th 
Fig. 10. Precipitation over the United States. The different shadings show the precipitation in 
inches as an average over a period of years (from Conservation in the United States by Gustafson et al., 
Comstock Publishing Co., 1939). 
