76 
R. KOCH. 
ogenic influence of the bacilli prepares to spread it self out upon the neighbor¬ 
ing cells existing within a certain circuit. Whether they have proceeded from 
cells already present in this place in consequence of the attraction exercised by 
the bacillus itself, or rather by the materials produced.by it and diffused into the 
surroundings, all cells situated within a definite region change into epithelioid 
cells. The cell containing the bacillus suffers still greater changes. It grows 
constantly larger, while at the same time the nuclei constantly increase, and it 
finally attains the shape and size of the familiar giant cells. That the develop¬ 
ment of the giant cells really goes on in this manner can be seen from suitably 
prepared sections, which show all stages of development from simple epithelioid 
cells with one bacillus to the completely developed giant cell with many nuclei 
and many bacilli. As most suitable for the study of the development of giant 
cells I should consider the tuberculous tissue of cattle and horses, which is espec¬ 
ially rich in giant cells and in which I have often seen the above mentioned 
transitional forms. The further fate of the giant cells is a varied one, according 
as the progress of the disease is rapid or slow. In the last case the number of 
bacilli enclosed by a giant cell is always a limited one. Usually there are only 
one or two. It is indeed scarcely to be thought that the bacillus found in a large 
giant cell is the same which caused the formation of the cell. One finds not in¬ 
frequently in a giant cell a bacillus which is no longer so intensely colored as 
other bacilli in neighboring gigantic cells; I have also seen cases in which the 
giant cell contains a dark and strongly colored bacillus, and beside it a second, 
very pale one, which without careful attention would be overlooked. Further¬ 
more I have sometimes found spore-bearing bacilli in the interior of giant cells. 
From all this I conclude that the giant cell is quite a durable formation, that the 
bacilli, on the contrary, do not possess such duration of life, and that they can 
only maintain themselves for a considerable time in giant cells, in that a new gen¬ 
eration follows a dying one. Sometimes they form spores in the interior of the 
giant cells, and in this case leave behind them the germs of a later generation. 
But often enough the vegetation of the bacilli in the cell appears to die out and 
the empty cell then remains as a monument of their former presence. When 
one, as is often the case in a tuberculous tissue, finds quite numerous giant cells, 
and among them only comparatively few supplied with bacilli, one can then take 
for granted that many of the apparently empty gigantic cells contain spores of 
tuberculous bacilli; others, on the contrary, mark the places of former vegetations 
of bacilli, and one is tempted to institute a comparison with a volcanic region in 
which occur not only single active volcanoes, but a great number slumbering for a 
time, or completely extinct, these latter nevertheless bearing unmistakable marks 
of their former activity. 
As to the fate of giant cells when the bacilli in them increases rapidly, we 
have already spoken. In this case the result is exactly opposed to the one just 
described ; the giant cell is the conquered party; it is, as it were, burst by the tu¬ 
berculous bacilli forcing themselves through the wall of nuclei. Its nuclei 
perish, dissolve themselves into little grains, and the cell perishes. 
How it is that at one time the bacilli are conquered, or for a long time re¬ 
main confined to definite spots and barely hold their own, that at another time 
their number increases rapidly and all cell elements in their neighborhood quickly 
