The Lung Tissue in Mice Infected by Tubercle Bacilli 



249 



Most of the material presented is from such an 

 area in an animal killed eight weeks after infection. 



In the electron microscopic picture most obvious 

 are the great number of cells containing lots of black 

 homogeneous, rounded granules about 0.5 to 1 // in 

 diameter. Some of them have been recorded with 

 surrounding concentrically layered membranes, each 

 with a thickness of about 100 A. 



In the neighbourhood of these cells are others 

 filled with vacuolar structures of about the same size. 



In most of the cells containing these black granules 

 a rather high number of tubercle bacilli and often 

 some other characteristic structures described below, 

 have been found. They are supposed to be stages in 

 the degeneration of cells, in this experiment caused 

 by the tubercle bacilli. 



One type of these granules (A) is rounded with a 

 fine-granulated ground substance, rather poor in 

 contrast and of varying size about 0.2 0.5 //. 

 Within these granules are sometimes seen rounded 

 clusters of strong osmiophilic granules (B), 50-1 00 A 

 in size. A more complicated type of granules (C) 

 about 0.5 to 1 // in width and often of a charac- 

 teristic shape is also observed. This structure seems 

 to consist of a great number of peripheral concentri- 

 cally layered membranes, approximately 100 A in 

 width and a medulla consisting of small osmiophilic 

 granules, the most peripheral of which seem to be 



Fig. 2. Tubercle bacilli in a cell containing black granules 

 within vacuoles. The picture is supposed to demonstrate a 

 later stage of cell destruction. Magnification 20.000. 



Fig. 1. Clusters of small B-granules in an A-granule. The 

 very characteristic C-granule with its many concentric 

 membranes is also seen. Two tubercle bacilli (tbb) are seen. 

 The picture is supposed to demonstrate an early stage of 

 cell destruction. Magnification 46,000. 



arranged in parallel rows. The C-granules are some- 

 times more or less covered by a black osmiophilic 

 homogeneous substance. 



The different types of granules just described have 

 been recorded in the same section (fig. 1) as well as 

 some others which according to their ultrastructure 

 (number of concentric membranes and granulated 

 centers etc.) very possibly could be intermediate 

 stages. 



The different granules and vacuoles are supposed 

 to be stages in the degeneration of cells, where 

 "A-, B-, and C-granules" are found in the early 

 stages. The black granules could be intermediate 

 products, which later on are dissolved leaving vacu- 

 oles in the eel I. (The eel Is containing the black granules 

 are In this case supposed to be macrophages.) 



The degeneration is believed not to be absolutely 

 specific for the tuberculous inflammatory reaction. 

 The reason for this conclusion is that a very few 

 opaque granules of about the same size can be seen 

 in normal lung tissue cells and \o a cerlaiii extent 

 have also been observed in lung tissue from pneumo- 

 coccus-infccted mice. 



This experiment, howe\er. has shown a distinct 

 increase in the number of the characteristic black 

 granules. My interpretation is, that normally cells 

 are to a certain extent degenerating and dying. In 

 the infected tissue, however, where the infecting 

 agent is localized in the cell proper, this degeneration 

 is proceeding rapidly and intensively thus giving very 

 obvious alterations. 



