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PROCEEDINGS OF THE SCIENTIFIC ASSOCIATION. 
fluences ; on the other, by assisting in the decomposition 
of organic matter, it creates those very influences, as the 
gazeous substances evolved from such decomposition act as 
a poison. Supposing causes of insalubrity to be perma- 
nent, the constitution, not of individuals only, but of whole 
generations may be profoundly modified. The inhabitants 
of marshy districts are sallow, weak, inactive, and die 
young. 
By the hygienist atmosphere should be regarded as an 
immense reservoir from which plants are supplied with 
carbonic acid, and animals with oxygen. It is, however, 
liable to changes which arise from the action of both the 
vegetable and the animal life. Man is connected with at- 
mosphere in various ways : but that connection is neces- 
sary, incessant. If from the providential stability of its 
chemical composition it is the pabulum vitce , it may, under 
certain circumstances, become a fruitful source of diseases. 
Dampness, want of ventilation, overcrowding in insalu- 
brious lodgings are incompatible with health. No doubt 
that certain maladies owe their existence to the toxical ac- 
tion of contaminated air. As a general rule, effluvia give 
birth to fever in all its various forms and react on the 
digestive and nervous systems ; miasms evolved from ani- 
mal matter undergoing putrefaction give rise to diarrhoea 
and typhoid fever. 
The principles to be met in the atmosphere are, either 
inherent, as heat, electricity, light and aqueous vapours ; or 
accidental. Man is, to a certain extent, powerless against 
the former, whilst he can, within certain limits, control the 
latter. Evidently no measures that can be suggested will 
ever control the influence arising from the heat, light and 
moisture dependant on our geographical position ; but we 
