426 Proceedings of the Loyal Physical Society. 
Here we meet with anemia, malaria, diseases of the gastro- 
intestinal tract, hepatitis, dysentery, diarrhcea, beri-beri, 
dengue, yellow fever, etc. Various diseases, however, are 
not met with, such as typhus, plague, goitre and cretinism, 
and, for the most part, diseases of the kidneys. It is 
obvious that inhabitants of the temperate zone dwelling in 
this lowest or hot zone must be injuriously affected by the 
climate, and probably the greatest injurious effect they sus- 
tain is due to the heat and equable temperature, the tonic 
effects of the cold season being sorely missed, in consequence 
of which there is a gradual sinking of the vital energy. 
Moisture is the next injurious element, for dry heat is much 
less injurious to such emigrants than a hot moist atmosphere. 
The character of the soil exerts a not inconsiderable in- 
fluence, low-lying clayey soil, soil rich in mould, and 
alluvial soil, acting injuriously; dry or sandy soil being 
less injurious. If the soil be marshy, temperature is lowered, 
and it is found that by draining the soil the temperature will 
be raised 2 or 3 degrees. The drier the soil the greater the 
heat during the day, the greater the cold by night, owing to 
the rapidity with which the soil cools by radiation. Vegeta- 
tion also influences the salubrity of these regions, for where 
it is abundant the temperature will be more equal, the 
vegetation preventing the sun from heating the ground, and 
also preventing radiation during the night. Lakes also 
exert an influence, by preventing much variation between 
the temperature of day and night. 
A good deal is written concerning the high rate of 
mortality in tropical regions, but in comparing the salubrity 
of areas in the temperate zone and in the tropics, it 
is often left out of mind that much of the salubrity of 
Europe is due to artificial causes—to the prevention of 
disease, to sanitary measures, to the care of the sick and 
infirm, and to the superior medical knowledge of our law 
and civilisation. This fact can be at once appreciated when 
we consider the state of health and rate of mortality in 
different European states; and when we find such marked 
contrasts as are presented in Great Britain and Russia for 
instance, we observe that locality alone does not cause the 
