FEBRUARY 2, 1912] 
it therefrom by an improved technic of 
isolation. Before I show you any slides or 
describe further the discoveries made it 
will be necessary for me to refer briefly to 
the nature of cancer and certain other 
malignant animal diseases. 
When I first called attention of members 
of the American Association for Cancer 
Research to crown-gall in 1909, the reply 
of some of the members was that while I 
had demonstrated crown-gall to be a very 
interesting disease it was evidently a gran- 
uloma, and not a true tumor. With this 
conclusion I can not agree. That you may 
understand why crown-galls are not gran- 
ulomata I wish briefly to call your atten- 
tion to the phenomena occurring in such 
diseases. As example of a granuloma, we 
may take tuberculosis. We have in this 
disease a focus of infection and source of 
irritation in the presence of a microorgan- 
ism. Against this organism the body reacts 
with the formation in the immediately sur- 
rounding tissues of cell growths not unlike 
those which occur in the bottom and sides 
of wounds, namely, granulation tissue, 
hence the name granuloma. In this man- 
ner nodular growths arise, but these nodu- 
lar growths are limited in extent of tissue 
involved, are produced from the tissues 
immediately surrounding the bacterial 
nest, are not vascularized, and soon become 
disorganized in their interior. In tuber- 
culosis the blood vessels occurring natur- 
ally within the attacked area are obliterated 
and excluded from the tubercle; in certain 
other granulomata, e. g., syphilitic gum- 
mata, the vessels are not obliterated, but 
they are distinct in other ways, e. g., en- 
closed in a fibrous capsule. The disease 
is carried from place to place within the 
body by the migration of the microorgan- 
isms, either in the blood stream or the 
lymphatics or in some other way, e. g., 
through the digestive tract. Wherever 
SCIENCE 
163 
these migratory organisms lodge they set 
up or may set up similar irritations with 
the production of similar nodules of gran- 
ular tissue, the same being an effort on the 
part of the infected animal to overcome 
the disease. The point which I wish spe- 
cially to emphasize is the fact that in these 
secondary infections the granular tissue 
which develops is formed out of the par- 
ticular organ in which the parasites happen 
to lodge, and does not consist of cells 
brought to it from a distance. 
In this respect cancers are quite differ- 
ent. Parenthetically I might stop here 
long enough to say that I shall for the pur- 
poses of this address use the term cancer in 
a loose, general sense for all malignant hu- 
man tumors. First, because the crown-gall 
which I have studied seems to partake of 
the nature of different types of malignant 
animal tumors, and because I believe that 
when the cause of malignant animal 
tumors is discovered we shall find that 
many of the hard and fast lines of separa- 
tion which the animal histologists have 
erected between sarcoma, carcinoma, etc¢., 
will be found untenable. 
In cancer we have an enormous multipli- 
cation of certain tissues of the animal 
(epithelial, connective, etc.) which by con- 
tinued growth crush and disorganize the 
surrounding tissues. These growths are 
more or less highly vascularized, and new 
vessels are formed as the tumor develops, 
but not to an extent sufficient to carry on 
the growth beyond a certain point. Usually 
there is a great excess of parenchyma cells 
in such a tumor and the blood vessels are 
not sufficiently numerous to nourish it 
properly, so that after a longer or shorter 
period (months or years) portions of it dis- 
organize often into open wounds which are 
then readily infected by all sorts of second- 
ary organisms with all the well-known 
disastrous results. This then is one strik- 
