Jan. 29 # 1917 
Mechanism of Tumor Growth in Crowngall 
167 
shown, by the surface tension of the cells. This is due, he thinks, to 
lipoids or fatty bodies present in their surface membrane. If one changes 
the surface tension of egg cells by the introduction of alkalies or fatty 
acids or even by punctures, growth takes place in the absence of fertiliza¬ 
tion, and a new animal (the fatherless frog or sea urchin) results. This is 
the problem of starting the normal physiological growth of a whole 
organism from an egg in the absence of sexual impact and it has been 
solved by withdrawing water from the surface of the egg cell. This has 
been done in some species by pricking the eggs, and in others by increasing 
the osmotic pressure of a surrounding fluid. In malignant tumors the 
problem is one of explaining a continuous and excessive local growth , 
abnormal in that it is outside of physiological control, but it is, I believe, 
a problem to be solved in the same way, viz, by showing that the over¬ 
growth is due to a removal of the local growth inhibitions by local increase 
of osmotic pressures. As I now see it, tumor growth is not at all a chem¬ 
ical phenomenon, but rather a purely physical one, a matter of varying 
molecular vibrations, a development dependent on locally increased 
osmotic pressures which cause a movement of water and foodstuffs into 
the affected area. In crowngalls the removal of growth inhibitions is 
brought about, I think, by the physical action of substances liberated 
within the tumor cells as the result of the metabolism of the imprisoned 
bacteria. Occasionally in this paper I have used the convenient word 
“stimulus” in an unqualified way, but by it I mean always and only the 
remover of an inhibition . 
If the cell proliferation in crowngall is due to substances liberated 
within the cell by the parasite, as it seems reasonable to suppose, they 
must be substances either identical with or at least not differing greatly 
in their physical or physiological action from those acting on the non- 
parasitized cell during normal growth and division. Of this there can 
be little doubt for several reasons and especially for the reason that 
there is no evidence of chemical injury either in the tissues surrounding 
a crowngall or in the tumor cells themselves, since they grow and multiply 
with a rapidity only to be compared with that of the cells of normal young 
tissues. This at once removes from consideration all actively poisonous 
(killing) substances and greatly simplifies the problem. 
Various weak (dilute) poisons are known to cause cell proliferations in 
plants—that is, copper salts (7, 8), vaseline and paraffin oil (9), * 1 salts of 
1 Schilling’s interesting paper (9) was received at the Department of Agriculture in November, 1915, but 
I did not know of its existence until October of the following year—i. e., after my own experiments were 
completed, except for a few repetitions and some tests with poisons in great dilution. His results (numer¬ 
ous large-celled intumescences) were obtained by vaselining or paraffining the surface of twigs of various 
species: Aesculus, Sambucus, Syringa, Artocarpus, Philodendron, Ribes, Spirea, etc. Since this note was 
in type I have discovered that Schilling’s work is only a repetition and extension of work published in 1910 
by the Russian botanist, P. Wisniewski (22). 
