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contains cases in wliich the occurrence of tumour-like growth or true tumours in the organs
of animal or man, has been found coincident with the presence of helminthes (especially tre-
matodes or nematodes) and a sort of causal relationship might probably exist bere, in analogy
witb the now elucidated power of the Bilharzia worm to produce cancer in the urinary blad-
der of man. Borrel, moreover, has put forward the hypothesis that the development of cancer
in mice and rats is due to an unknown virus, transmitted by various parasites, among which
nematodes; and according to Haaland there is evidence that the presence of nematodes
in the subcutaneous tissue of the mammary gland in mice might be made responsible — at
least to a large extent — for the frequency of inflammatory processes, associated with patho-
logical changes of adenomatous and cystical character, from which a true cancer can develop.
In order now to make out, whether a causal relationship might exist between the nematode
found in the 3 rats from Dorpat and the pathological changes of their stomachs, a series of
examinations were carried out. The results of these investigations having been published in
full extent in "Zeitschrift fiir Krebsforschung"^), only a shorter summary will be
given here.
Subcutaneous and intraperitoneal transplantation of tumour-cells from 2 of the 3 Dorpat
rats into normal rats of various species gave negative results. In experiments with rats fed
on tumour-cells no papillomatous growth was noted, and in rats, isolated for a longer time
(until one year) in the same (uncleaned) cage, in which had been kept the 3 rats from Dorpat
neither pathological changes of the cardiac portion of the stomach nor nematodes were observed.
In faet, no tumour-like growth of the stomach was found in the rats of the Institute
except in the 3 rats already mentioned, which harboured the nematode and most Ukely were
imported to Denmark from Dorpat,
Numerous examinations were made of wild rats from various localities in Copenhagen or
from the neighbourhood and of white and black and white rats from different laboratories,
but neither papillomatous growth nor nematodes similar to those which had initiated the investi-
gation were observed.
Thus, pathological changes as the described no more than the nematode seemed to be
known here in Denmark and the faet that the feeding experiments on tumour material, con-
taining nematodes, had not been successful, might perhaps be due to an insusceptibiUty of
Danish rats.
Another possibiUty — however — appeared to be still more obvious: Instead of being
directly infective the nematode might be wanting a host, in which the embryos of the eggs
could attain a higher stage of development, which would make them infectious to the rat.
As according to a report made by Galeb in "Comptes rendus des seances de l’Académie des
Sciences", Tome 87, 1878, it was possible, that cockroaches (Periplaneta orientalis) were able
to serve as a host, investigations were made on several wild rats from a locality in Copen-
hagen where great numbers of P. orientalis were at hånd.
Neither nematodes nor tumour growth, however, was found in any rat, and feeding ex-
periments on normal rats with cockroaches from this locality also turned out negative.
A better result was given by some examinations made in another locahty, a sugar
refinery, which harboured lots of rats and cockroaches, although these were not P. orientalis
but P. americana.
’) i-Lc.
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