632 
RECIPROCAL INFLUENCE OF ANIMALS. 
My researches, I regret to say, have not been so satisfactory 
as I could have desired in a matter of this kind, but the 
pathologists, travellers, and others who have noticed this par¬ 
ticular morbific quality are scarce, and their writings are not 
readily accessible. 
The human species appears to afibrd us the most striking 
examples, possibly because observers have been more nume¬ 
rous and intelligent than in the case of the lower animals. 
One of these is given by my friend Mr. Bates, in a work re¬ 
cently published,* and is a startling instance of the myste¬ 
rious manner in which disease arises from the approximation 
of two races of men. This distinguished naturalist, when on 
the Upper Amazons, writes, The Passes are a slenderly- 
built and superior race of Indians, distinguished by a large, 
square, tattooed patch in the middle of their faces. The 
principal cause of their decay in numbers seems to be a dis¬ 
ease which always appears amongst them when a village is 
visited by people from the civilised settlements—a slow fever, 
accompanied by the symptoms of a common cold, ^ defluxo,’ 
as the Brazilians term it, ending probably in consumption. 
The disorder has been known to break out when the visitors 
were entirely free from it; the simple contact of civilised 
men, in some mysterious way, being sufficient to create it. 
It is generally fatal to the Juris and Passes; the first ques¬ 
tion the poor, patient Indians now put to an advancing canoe 
is, ‘ Do you bring defluxo?’ It fills one with regret to learn 
how many die prematurely of a disease which seems to arise 
on their simply breathing the same air as the whites.” 
Langsdorfjf many years ago, stated that the Maynas, 
another race of Indians, constantly suffered from catarrhs and 
dysentery if Europeans came amongst them. 
Humboldt J says that the great epidemics of yellow fever 
at Panama and Callao were “ marked,” because they occurred 
on the arrival of ships from Chili, owing, it was supposed, 
to the people from that temperate region first experiencing 
the fatal effects of the torrid zone. In the Port of Panama, 
as at Callao, the commencement of the great epidemics is most 
frequently marked by the arrival of some ships from Chili,—^ 
not that this country, which is one of the finest and most healthy 
on the globe, can transmit a disease which has no existence 
there, but because its inhabitants, transplanted to the torrid 
zone, experience to the same degree as people from the north 
* The ‘Naturalist on the Amazons/ pp. 194, 240. 
t Schnurrer, ‘Pathologie/ p. 266. 
f ‘ Neu Spanien, vol. iv. 
