108 
R. KOCH. 
herds. This proceeding can complete itself in various ways. The bacilli can 
get into the larger blood vessels of the lungs, be strewn over the whole body 
in greater or lesser numbers by the course of the blood and cause miliary tub¬ 
erculosis. Then, according to all appearance, the bacilli have the power of 
spreading themselves also byway of the course of the lymph, of forcing them¬ 
selves into the bronchial glands and causing secondary tuberculous changes. The 
bacilli conveyed from the cavities into the air passages find by far the most fre¬ 
quent opportunities of fixing themselves in other places. Oftentimes they nestle 
themselves in other parts of the air passages and more especially into the larynx. 
Often if the sputum be swallowed they plant themselves in the intestinal 
passage. 
The usual course of the phthisis must then be most affected when the ba- 
cilli-bearing pus from the cavities is on the way to be conveyed outward by 
the bronchioe, but by some unfortunate disturbance of the motions of respira¬ 
tion is again aspirated and brought into parts of the lung until then healthy. 
When only a slight quantity, poor in bacilli, is aspirated, it can only bring 
about the beginning of a comparatively small number of infectious herds. 
These will gradually grow and develop into cavities according to the place 
that the bacilli-bearing masses reach, sometimes in the immediate neighbor¬ 
hood of the mother herd, sometimes some distance from it, even in the other 
previously healthy lung, and will from small beginnings grow just as slowly 
as the first tuberculous herd. But as soon as considerable quantities of the 
bacilli-rich contents of the cavities are breathed in, and wide-spread parts of 
the lung are overflowed, as it were, with infectious material, as appears not 
seldom to be the case, then the formation of single tuberculous knots is not 
the first step, but tuberculous infiltrations arise which show us by the lobed 
and even lobuled (lobuliire) arrangement that they came from the respiratory 
passages. The penetration of the tuberculous bacilli en masse has not as a 
consequence heaps of closed cells and the formation of giant cells, as is the case 
when individual bacilli appear, but necrosis of the component parts of the cells 
in the attacked tissue spreads widely and with comparative quickness. In 
consequence wide-spread caseous degenerations form in many places, also 
rapid dissolution of the tissue, with development of cavities which bear another 
character than those formerly described. 
While these cavities possess compact, firm walls in which are found giant 
cells and scattered tuberculous bacilli, the walls of cavities formed in the de¬ 
composing and widely caseous lung tissue are permeated by a thick bacilli 
vegetation. They do not consist of condensed callous tissue, which only 
melts away slowly under the influence of the bacilli, but the wall allows us 
still plainly to recognize the structure of the alveoli which are filled with the 
caseous substance rich in bacilli, but are in the act of losing their coherence, 
and falling to pieces. These conditions are usually described as caseous pneu¬ 
monia, acute phthisis, etc. 
The most various combinations of these two just described processes, that 
of a tuberculous herd proceeding from a single infectious herd and spreading 
slowly, and the caseous infiltrations arising from a flood of infectious material, 
unite to give a most varied conception of the tuberculous destruction of the 
lungs covered by the general name phthisis. 
