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105
animals other than man are identical culturally, microscopically,
and in their effects upon the tissues of experimental
animals, with bacilli from certain cases of tuberculosis in
the human subject.
2. Referring to the anatomical origins of the human
viruses which have been investigated, attention is called to
the fact that in all parts of the human body, and in human
sputum, collected with due precautions to avoid contamination
through food, tubercle bacilli have been found which
culturally and in histological effects are identical in every
respect with the tubercle bacillus commonly present in
the bodies of tuberculous cattle and swine.
3. It is found that many of the viruses of human
origin grow with greater cultural luxuriance and produce
less histological damage in the organs of certain experimental
animals than the bacilli commonly obtain.ed from
cattle and swine.
4. In the majority of cases the examinations of the
cultures and the animal tissues which have been received
at different stages during a protracted series of experiments
with the same virus have shown that the original characteristics
of the virus were remarkably stable.
5. Hence, to such extent as it may be supposed that
such series of experiments are comparable to what takes
place in a human body infected with tubercle bacilli, the
result supports the view that changes in the characteristics
of a virus do not readily or rapidly take place in the human
body.
6. But there have been examined in addition certain
other viruses which in respect of the details reported on,
hold an intermediate position between the viruses usually
obtained from human sources, and those of common animal
origin.