iETIOLOGrY OF TUBEKCULOSIS. 
57 
when the very smallest amount of the blood of an animal dying of inflam¬ 
mation of the spleen is inoculated into another animal, said animal invariably 
dies of the same disease, and it also contains the little rods, the so-called “bacilli” 
of inflammation of the spleen. This does not prove, however, that by the 
inoculation of the little wands, the disease was communicated. In order to know 
whether the bacilli, and not other components of the blood of inflammation 
of the spleen, produces said inflammation, the bacilli must be separated from the 
blood, and be inoculated alone. 
The isolation of the bacilli can be ascertained with most certainty by contin¬ 
ued cultivation apart from all other things. To this end, a small quantity of 
blood containing bacilli is placed upon some fixed nutrient soil, on which the 
bacilli are able to grow, for instance, nutrient gelatine or boiled potatoes. Here 
they soon begin to increase very rapidly, while the other components of the blood, 
corpuscles and serum, remain unchanged. After two or three days, when the 
bacilli have formed a dense mass of spore-holding threads, the smallest possible 
of the no longer blood-red, but whitish looking mass, is taken and again placed 
upon nutrient gelatine or boiled potatoes. The bacilli increase in exactly the 
same manner as in the first planting, and form a dense white mass on the potato, 
and already in this second transplanting the most careful examination with the 
microscope will scarcely show any traces of the other components of the blood. 
In like manner the continued transplanting is carried on. After the third or 
fourth, the bacilli may be considered free from all other parts of the blood, which 
at first were planted with them. If the transplantations now are repeated twenty 
or fifty times, or still oftener, then it may be concluded with all imaginable cer¬ 
tainty, that not the least taint of the disease clings to the bacilli. Even inter¬ 
nally they could hide nothing of that kind ; for the finest planted bacilli are also 
no longer present, and their descendants for many generations have obtained the 
necessary material for their growth from their fostering soil, the potato. The 
pure breed obtained in this way has no connection with the diseased organism 
from whose blood the first planting came, and with the products of disease, which 
belong to animal metamorphosis. Nevertheless, as soon as they are inoculated 
into a healthy animal, they produce the fatal disease. The inoculated animal 
sickens as quickly and with the same symptoms as if it had been inoculated with 
blood fresh from a diseased animal, or had spontaneously become diseased with 
inflammation of the spleen, and in its blood appear the same innumerable 
bacilli as in the natural disease, which have the same properties as the well known 
bacilli of inflammation of the spleen. In view of these facts, there is no 
other explanation, than that said bacilli are not an accompaniment of inflam¬ 
mation of the spleen, but the real cause of this disease. Now inflammation 
of the spleen does not always present the same clinical appearance; its form 
varies in the different species of animals; in the case of man it can run its 
course with the symptoms of a general infection, without prominent local dis¬ 
turbances, or it can remain purely local and confine itself to a certain point on 
the outer skin, on the gut, or on the larynx. Nevertheless also in these cases, if 
the characteristic bacilli are found in the diseased places, we must consider them 
as the cause of the disease ; for their disease-producing qualities are known to 
us, and we cannot very well imagine that in the tissues of the same organism the 
