78 
R. KOCH. 
of which the same is formed. If a substance containing spore-bearing tubeicu- 
lous bacilli be examined in the uncolored condition and in less strongly refractive 
liquids, the bacilli appear to be provided with brilliantly shining little bodies; 
these last can therefore not be vacuoles or simple gaps in the protoplasm of the 
bacillus, but must be genuine spores. 
After these remarks as to the universal qualities of tuberculous bacilli, I now 
turn to the description of their action in the various tuberculous processes. 
A. TUBERCULOSIS IN MAN. 
I.—Miliary Tuberculosis. 
Nineteen cases in all were examined in which the tubercles were found in 
the form of miliary and sub-miliary little grey knots, mostly provided with a 
whitish or weak yellowish centre, scattered in several organs, lungs, brain, liver, 
spleen and kidneys. The bacilli were wanting in the tuberculous knots in no 
one of these cases. The smaller and younger the knots were, so much the more 
plentiful were the bacilli, and they were thickest at the centre. As 
■eoon as the middle of the little knot will no longer take nucleus coloring, as 
soon, therefore, as the caseous degeneration begins, the number of bacilli de¬ 
creases immediately. In the larger knots, whose centres had already experienced 
a far-reaching caseous change, few bacilli were to be found, and those only to be 
found between the nuclei of the epithelioid cells occurring in the periphery of the 
knot. Now and then one finds in the giant cells occurring on the border of the 
caseous herd, single bacilli or groups of the same. A noticeable fea¬ 
ture which re-appears in the chronic processes of the lungs is this, that 
most giant cells contain black pigment grains beside which the bacilli are 
still easily to be distinguished. In other organs I have not seen such 
pigment-bearing giant cells, and their presence appears to be limited to the lungs. 
From the analogy of other results obtained from the lungs of swine and other 
animals, to be mentioned later, I might suppose that we here have before us 
giant cells which originally developed in the interior of an alveolus and took into 
themselves the pigment of the perishing cells present in the alveolus. This view 
is taken by Watson Cheyne on the ground of direct observations of giant cells 
which were found in alveoli of the human lung. (See Practitioner, April, 1883). 
These cells, which first developed in the alveoli next to the little knots, are after¬ 
wards taken up by them as the knots extend. In many of the older knots the 
bacilli appear to have vanished completely. Nevertheless, we must remember 
that the prepared sections of the larger tubercles always contain only fragments, 
and that if the bacilli are wanting their absence from the whole knot is not there¬ 
by proved. The relations here are similar to those formerly described in regard 
to the giant cells, that is to say, that beside those knots which still contain abun¬ 
dant bacilli others occur in which the bacilli have either entirely vanished or 
have left spores behind them. Nevertheless, if a sufficient number of sections 
are examined, one almost always finds spots rich in bacilli, and it would not be 
right from the results of a few specimens to give a judgment as to the presence 
or absence of bacilli in miliary tubercles. 
In miliary tuberculosis of the liver and spleen, I have seen bacilli almost ex¬ 
clusively in the giant cells. Especially in the spleen, beside completely developed 
