958 The American Naturalist. [November, 
On this point we have the altogether antiquated classification 
of diseases into " Contagious, infectious and sporadic," which 
should be replaced to-day by speaking of them as : 
Extra-organismal, or exogenous ; 
Intra-organismal or endogenous ; and, 
Sporadic ; that is of undemonstrable origin ; 
or, in other words, from the etiological point of view we can 
logically classify diseasesonly according to the primary origin of 
their specific cause. 
A recent reviewer in the New York Medical Record says of 
my " Investigations of Cattle Diseases in Nebraska," which in- 
cludes some researches made upon alcoholic material from yellow- 
fever patients, that said work " contains much that is interesting, 
but is, unfortunately, very controversial in tone." 
What nonsense ! How can one ever hope to establish truth 
in the face of error but by controversy ? To my mind, the more 
grievous the error, the more grievous the necessity for correct 
controversy, and there are some very grave reasons in this country 
why the controversy should be turned into a very severe battle 
for the truth, so far as original research is concerned. 
Going back to our original differentiation for a moment, 
Hucppe has come to the same idea when he speaks of the micro- 
organismal causes of disease as " obligatory parasites," by which 
he means that such etiological moments are primarily bound on 
the conditions offered by some form of animal life for their exist- 
ence and continuous development; or, in other words, such 
diseases are " endogenous " in origin, to speak with Pettenkofer, 
or intra-organismal in origin, as I have termed it. An endogenous 
disease is one which, so far as we can historically trace its genesis, 
has found and still finds its locus of primary origin for each new 
outbreak or extension of the disease, in a diseased individual of 
some given species of animal life (and never in any other way) ; 
and then passes directly from the diseased individual to another 
susceptible healthy one, either by direct contact, or cohabitation, 
or by contact with some effluvia which has either come directly 
from, or been in immediate contact or relation with, such a diseased 
individual. 
