54 
R. KOCH. 
/ETIOLOGY OF TUBERCULOSIS. 
By Dr. R. Kocn, Privy Councillor. 
(Translated by Rev. F. Sause.) 
( Transactions of the Massachusetts Veterinary Medical Association.) 
A series of investigations of the ^Etiology of Tuberculosis which I have been 
making within the last few years have led me to results which were first reported 
before the Physiological Society of Berlin, March 24th, 1882 (Berliner klinische 
Wochenschrift, 1882, No. 15). My communications at that time, however, could 
only embrace the most important points, while the more minute description of the 
attempts was necessarily reserved for a detailed report. Since then, by continued 
investigations, many gaps have been filled and new matter added. The report of 
my labors in the investigation of the aetiology of tuberculosis, completed and en¬ 
larged by these researches, is given in the following. 
The question whether tuberculosis is a disease dependent upon transmitted 
disease-germs can be approached in different ways, as this has in fact been done. 
It has been attempted to secure certainty, partly with the aid of clinical observa¬ 
tions, partly by means of anatomical and also by experimental investigations. 
Most uncertain are the results of the experience gathered at the sickbed. It is 
true, cases occur in the experience of every physician with fair practice, in which 
he cannot fail to see a transmission of tuberculosis from one person to another. 
Then, however, follow numerous cases in which every possibility of infection seems 
to be excluded. Attempts have been made repeatedly to prove the contagious 
nature of phthisis, but they must be looked upon as failures, as such views have 
never found acceptance among scientists. Some clinical authorities, to be sure> 
have not lost view of the possibility of contagion, but on the whole physicians 
consider phthisis a non-contagious disease, proceeding from constitutional anom¬ 
alies. An indication of the infectious character of tuberculosis, which cannot be 
ignored, was given by pathological anatomy, when Buhl called attention to the 
connection of miliary tuberculosis with kiise-herden,* (a German technical term 
of which I do not know the meaning in the English language) and offered the prop¬ 
osition that general tuberculosis is to be looked upon as a disease which is 
brought about by the resorption of a virus present in the primary kiise-herd 
(cheesy-nodule), hence as it were, by auto-infection. As to the manner in which 
tuberculous virus spreads itself through the body, the discoveries of Ponfick in 
regard to the thoracic duct and of Weigert in regard to veinous tubercles in miliary 
tuberculosis have given light. However, these facts only prove the spread of tub¬ 
erculous virus in the body itself, without proving the transmission from one 
individual to another, in which latter the contagious nature really consists. With 
this last question experimental pathology has occupied itself in the most searching 
manner. The course taken in experimental investigations of the infectious nature 
of tuberculosis has been described of late very minutely, (cf, Johne, Die Ge- 
schichte der Tuberculose. Leipzig, 1883), so that I can omit the historical details 
and confine myself to a few remarks on the more inportant heads. 
*Cheesy^iiodules.—S. 
