Scientific Memoirs by
ones. As has been just indicated, however, we are here dealing with probabi
- l i t i e s o n l y , a n d a n y d e f i n i t e c o n c l u s i o n s c a n o n l y b e l o o k e d f o r a f t e r t h e o r g a n i s m s
have been studied while alive, and the various stages in their life-history
actually followed out in cultivations in suitable media.
The necessity for such observations is even more urgent in order to the
attainment of any definite answer to the question of the relation which they bear
to the occurrence of the disease with which they were in this case associated.
There are, however, certain points rendering it possible, if not even probable
that they actually were the specific causes of the disease. In the first place,
there can in regard to this specimen be no question of accidental entrance of
the parasites into the morbid tissues due to abnormal facilities presented by the
surface, for there was no ulcerated, raw surface present, and, on the contrary,
the horny layer of the epidermis was abnormally thickened and -resistent. This
in itself is in favour of a belief in their causal relation, as it is hard to see why
such bodies should specially attain access to the diseased rather than to the
healthy tissues unless some special structural facilities are provided in the former
for their doing so. The general features of the distribution of the parasites
also points in the same direction, for, as has been pointed above, they are
found to occur in numbers varying in fairly close correspondence with the degree
to which morbid changes have taken place. Much more significant, however,
is the fact of their frequent presence in sites where such changes are only
beginning to manifest themselves—in sites where small, isolated aggregations of
the neoplasm are interpolated among wide areas of normal tissue elements.
The circumstances under which the disease generally tends to occur—its
markedly endemic character, and specially its connection with the employment
of certain sources of water supply—are also strongly in favour of the causative
agency of bodies of the nature which those in the present case apparently
possess, as the plasmodia and zoospores of the Monadinæ are specially likely
to be present in water of special localities and of particular characters. The
distribution of specially large numbers of the parasites in special relation to the
remains of hair-follicles and in the neighbourhood of sweat-ducts is also of
some importance as it seems possibly to indicate these structures as special
channels of access to the substance of the tissues, and naturally they can only
serve as such so long as they retain their normal characters and have not been
pressed upon and obliterated by surrounding accumulations of neoplastic ele-
ments. The fact that the parasites occur in such deeply-seated areas as the
subcutaneous fat-lobules is quite in accordance with the clinical experience that
no superficial application of remedies is effectual in putting a stop to the disease,
and that free excision or penetrating destruction of the tissue of the diseased
area is necessary in order to do so.
It may, moreover, be pointed out that there are well-ascertained instances
in which parasites of monadinic' nature serve as the efficient cause of the de-