354. EPIDEMIC DISEASES. 
destructive, chiefly in consequence of the zeal with 
which inoculation was propagated ; between 50,000 
and 60,000 individuals having undergone the opera- 
tion. ‘The vaccine method was introduced in vari- 
ous parts of Mexico and South America at the com- 
mencement of the present century. Humboldt 
mentions a curious circumstance, tending to show 
that the discovery of our celebrated countryman, 
Dr Jenner, had long been known to the country 
people among the Andes of Peru. A negro slave, 
who had been inoculated for the small-pox, showed 
no symptom of the disease, and when the practition- 
ers were about to repeat the operation, told them he 
was certain that he should never take it ; for, when 
milking cows in the mountains, he had been affected 
with cutaneous eruptions, caused, as the herdsmen 
said, by the contact of pustules sometimes found on 
the udders. 
The frightful distemper called matlazahuatl, which 
is peculiar to the Indian race, seldom appears more 
than once in a century. It bears some resemblance 
to the yellow fever or black vomiting, which, how- 
ever, very seldom attacks the natives. The extent of 
its ravages is not known with any degree of certainty, 
and it has not yet been submitted to medical inves- 
tigation. .Torquedama asserts that in 1545 it de- 
stroyed 800,000, and 2,000,000 in 1576; but these 
estimates are considered by Humboldt as greatly 
exaggerated. 
A third obstacle to the progress of population in 
New Spain is famine. The American Indians, na- 
turally indolent, contented with the smallest quan- 
tity of food on which life can be supported, and 
living in a fine climate, merely cultivate as much 
