CHAPTER IX.. On Poisons, Miasms, and Contagions--Difficulties Besetting the

On poisons, miasms, and contagions--Difficulties besetting the questions as to their essential nature and origin--Poison of typhus, of yellow fever, and of the remittent fevers of hot countries--Their appearance at uncertain and distant periods in an aggravated form--Statistics of the recurrence of remittents in the West Indies--Light thrown by chemistry on the subject--Fermentation and putrefaction--Peculiar poisons--Distinction between a miasm and a contagion--Odour perceptible in sick chambers--Ozone, pp. 89–98