168 
to the cause of the abnormal growth,’ 
whereas in case of these overgrowths on 
plants we have definitely proved them to be 
due to the presence of an intracellular 
schizomycete which we have many times 
isolated and reisolated in pure culture and 
by means of which we can reproduce the 
disease at will. : 
The question now arises whether animal 
tumors might not be produced by means of 
the crown-gall organism. I might state 
here that while I believe cancer to be due 
to some intracellular microorganism which 
in its physiological peculiarities, action on 
the cell nucleus, ete., is like the one we have 
discovered, I do not maintain the over- 
growths in warm-blooded animals to be due 
to this particular organism, for the reason 
that its maximum temperature for growth 
(daisy strain) is a little under the blood 
temperature of such animals. In thinking 
over the matter it seemed to me not un- 
likely, however, that with this organism I 
might be able to produce tumors in cold- 
blooded animals, and so four years ago I 
attempted to do it. I will show you only a 
slide or two made from an inoculated fish. 
I used for this purpose brook trout and in 
a very considerable portion of my inocula- 
tions I sueceeded in producing ulcers in the 
deeper tissues where the needle entered. 
In this instance the needle entered the 
belly wall of the fish. The wound healed 
externally, but at the end of 21 days when 
the trout was dissected there was a well de- 
fined: inner growth (proliferation nodule) 
in the connective tissue between the muscles 
with formation of giant cells. There were 
also when dissected two external sore spots, 
7<¢Some unknown force, the essential nature of 
which has so far completely escaped our knowl- 
edge and our comprehension, is capable of calling 
forth this latent power of proliferation, and the 
germ [cancer cell] begins to grow out of itsclf, 
like a seed that has been buried in the ground.’’ 
(Diirek.) 
SCIENCE 
[N.S. Vou. XXXV. No. 892 
one below the pectoral fin and the other 
below the anal fin, both of recent occur- 
rence, but no throat or gill ulcers in this 
fish. Similar growths were obtained in 
the eye-socket. I showed sections cut from 
one of these ulcers to one of the most 
distinguished research workers on cancer 
in this country and he said ‘‘if we had this 
in man we should eall it sarcoma.’’ 
(Slides exhibited.) I propose to repeat and 
extend the work on trout and therefore will 
say but little about this phase of the in- 
vestigation. 
In conclusion I wish to call attention to 
some of the peculiarities of the microor- 
ganism (Bacterium tumefaciens) as deter- 
mined by our cultural work. As well 
known to many of you, we prosecuted our - 
studies upon the crown-gall for two years 
before we were able to isolate the parasitic 
organism. ‘Ten years previous to this I 
spent six months on the subject with a sim- 
ilar negative result. Two obstacles of 
which we were unaware blocked the way. 
In the first place the organism in a viable 
form occurs in the tumor tissue of the daisy 
in small numbers only. If inoculations 
are made from crown-gall tissue, using 
about that amount of tissue we are accus- 
tomed to use for other bacterial plant dis- 
eases, and also for many animal diseases, 
the chances are that no colonies of the 
parasite will be obtained upon the plates. 
I have no doubt now that we made dozens 
of plates—yes, I might say dozens of sepa- 
rate sets of poured plate cultures, on which 
not a single colony of the right sort de- 
veloped. It was only when we learned to 
inoculate our bouillons and agar plates 
with large quantities of the tumor material 
that we were able to obtain a sprinkling of 
colonies of the right organism. From a 
young, rapidly growing tumor it is always 
possible to obtain the organism with proper 
technic and sometimes in pure cultures, but 
