On the whole it appears evident, that races of. men acquire
predispositions to particular diseases by, a residence of several
generations in particular districts; Hence, then,'varieties of
predisposition are no proof, of diversity of originv
On this principle we may .explain, without reference to any
other hypothesis, the remarkable fact proved by the late researches
of Dr. Clarke, that Negroes and Malays are the vic-
tims of tubercular phthisis in much greater proportions than
other races b f men. By a calculation founded on data which
relate to the West Indian army of Britain, it appears, that
in every thousand deaths among the whites, chiefly as I suppose,
if not almost wholly, natives of Europe, one hundred
and twenty arise from pulmonic diseases, while in every thousand
deaths among the blacks, four hundred and sevehty-two
are attributed to~~the same cause. Dr. Clarke has likewise
shown, that in Ceylon, the deaths from phthisis in one thousand
deaths from all diseases, are in E u ro p e a i^ ^ ^ in Mal^its
58, in Caffers 146, in Indians 59 ; thus proving, that in other
races of men inhabiting tropical climates, the greater frequency
of tubercular disease is in as great proportion; whence he concludes,
that predisposition to such diseases is brought ferth
in the . organic structure of the human body by'residence in
hot. donates.
The excessive proportion of deaths by phthisical. disease
among the native races of hot climates, compared with those
which take place in strangers from cold countries, depends in
great part on the greater mortality produced among Europeans
by morbific causes peculiar to tropical regions, when compared
with that which takes place among the native inhabitants.
Negroes and other natives of hot countries bear with
comparative impunity many other agencies, whieh are highly
destructive of life among Europeans. We must not, however,
suppose from this fact* th a t the Negro is by nature exempt
from the susceptibility of those diseases which destroy so many
of the whites. Dr. Winterbottom assures us, that this is far
from true; that the native blacks of Sierra Leone often have
remittent and intermittent fevers, which run their course precisely
as they would do in Europeans, who, by what is
termed seasoning, have accommodated themselves to the climate.*
He adds, that the same diseases- are very common
-among the Negroes who were- brought from Nova Scotia to
live at Sierra Leone. This remark illustrates the nature of
that immunity from tropical diseases which some have ascribed
to Negroes as a specific character. Dr.. Clark of Dominica,
in- describing th e ydlow-rfever which- prevailed - in that
island in 1798-—6’, observes, thajt -thfe “ New, negroes,” who
had lately b’èen .imported from th e ' ebasbiof. Africa, were all
attacked by it...) The Negram who .hadbeen long in the town
or?oa the island escaped.^ I t ik wèlbknown; that the Negroes
■on the African eo,aè# suffer greatly .in unhealthy districts' from
dysenteries, diarrhoeas, and other diseases- which arise from
local C(auses!$ The native tribes of America are likewise subject,
according to Dr. Rush and'others, to remittent .and intermittent
.feye$4y dysenteries, and other- diseases' analogous to
those which attack Europeans under similar circumstances;
The yelltjwvfever appears to have been known in America long
^b@£bre the arrival \pf 'Europeans. ,Such, at least, is the result
'n f information obtained by M. de Humboldt. This -appears to
have been the p§stil§nee,which was teraied matlazahu#|| and
which ravaged the empire of the Aztecas before the arrival
of Cortes -and the Spaniards.
The native tribe^of America,'as we learn from ihe information
obtained by M. Say and Professor Keating, are likewise
subject to tbe same constitutional diseases as other races of
men. The account ' given b y these writers of the diseases of
the Sioux clearly proves that the morbific causes which affect
the constitution of Europeans, have the same influence, with
very slight differences which are easily accounted fqr, as those
of the native Americans. It appears, for example, that the
latter are subject to disorders of tbe nervous system, excited
by mental emotions: that cases of fits and of insanity are
attributed among them to disappointments in1 dove, and that
such disorders are so frequent as to be often feigned.
Similar observations respecting the diseases of northern
* Winterbottom, vol. ii. p. 14—22.
Medical Tacts, vol. viii. Winterbottom ubi supra.
± Winterbottom.—See Mr. Oldfield,' Memoir on the Medical History of tbe
countries visited in the late expedition to explore the Niger.