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by experience,, should relapse into former errors^ and recur to 
her odious habits, as in past ages, it is not to be doubted that 
a mutual recognition will take place, and she will again be 
visited by her abandoned child, who has been wandering a 
fugitive among kindred associates, sometimes in the mud cots 
of Egypt, sometimes in the crowded tents of Barbary, and 
sometimes in the filthy kaisarias of Aleppo.'’^ 
7. Yellow Fever is a contagious fever with a limited geo- 
graphical range. Its geographical limits, as regards the New 
World, are from about 43'^ N. lat. to 35° S. lat. ; and in the 
Old World from 44° N. to 8° or 9° S. lat. It is a common 
disease on board our ships stationed in the West Indies and 
off the west coast of Africa. As in the case of typhus, over- 
crowded and defective ventilation are the main causes which 
favour its origin and propagation, and, indeed, it is still a 
subject for investigation whether yellow fever may not be 
typhus modified by climate and other circumstances. One of 
the most recent and best authorities* on the disease thus 
writes Overcrowding in the between-decks of steam- 
ships seems to be the principal cause of the extreme fatality 
of the disease in the navy. What in this respect is true of 
typhus may with equal force be said of yellow fever. There 
is no such powerful adjuvant to the virulence of the poison, and 
to its power of propagation, as an unrenewed atmosphere, 
loaded with human exhalations.^^ 
8. Fiarrhoea is always more or less prevalent in this country 
during the summer and autumn. There is no reason to 
believe that epidemic diarrhoea is contagious, but there is 
a direct ratio between its prevalence and the temperature 
of the atmosphere and the absence of ozone. As the tem- 
perature rises, the cases increase in number, and as it falls 
they diminish, and the disease is always most prevalent in 
very hot seasons. Diarrhoea “may be due to many different 
causes, but its epidemic prevalence in autumn is chiefly 
accounted for by the absorption into the system of the pro- 
ducts of putrefaction of organic matter, either in the form of 
gaseous efiluvia or through the vehicle of drinking-water. 
9. Typhoid or Fnteric Fever is very commonly confounded 
with typhus, with which, however, so far as its origin is con- 
cerned, it has nothing in common. It is not, like typhus, 
confined to the poor, but it prevails among rich and poor 
alike ; and, indeed, there are some reasons for believing that 
the rich and well-fed are more prone to be attacked by it than 
the destitute. It is the fever by which Count Cavour, several 
members of the royal family of Portugal, and our own Prince 
* Dr. Gavin Milroy, President of the Epidemiological Society. 
