276 BACTERIA 



We may summarise the history of the pathology of 

 tubercle thus : 



1794. Baillie drew attention to grey miliary nodules oc- 

 curring in tuberculosis, and called them '* tuber- 

 cles." 



1834. Laennec described four varieties: miliary; crude; 

 granular ; encysted, 



1843. Klencke produced tuberculosis by intravenous in- 

 jection of tubercular giant cells. 



1865. Villemin demonstrated infectivity of tubercular 

 matter by inoculation of discharges; Connheim, 

 Armanni, Burdon Sanderson, Wilson Fox, and 

 others showed that nothing but tubercular mat- 

 ter could produce tuberculosis. 



1877. Living cells were found in tubercles, ** micro- 

 cocci '* (Klebs, Toussaint, Schiller). 



1882. Koch isolated and described the specific bacillus, 

 and obtained pure cultivations (1884). 



The Bacillus of Koch, 1882. Delicate cylindrical rods, 

 measuring 1.5-4 micromillimetres in length and about .2 // 

 in breadth; non-motile. Many are straight with rounded 

 ends; others are slightly curved. They are usually solitary, 

 but may occur in pairs, lying side by side or in small masses. 

 They are chiefly found in fresh tubercles, more sparingly in 

 older ones. Some lie within the giant cells; others lie out- 

 side; shorter in tissue sections of bovine tuberculosis, but 

 longer in the milk (Crookshank). 



When stained they appear to be composed of irregular 

 cubical or spherical granules within a faintly stained sheath. 

 In recent lesions the protoplasm appears more homogeneous, 

 and takes on the segmented or beaded character only in old 

 lesions, pus, or sputum. 



