BACILLUS TUBERCULOSIS 35 



to form small groups of such .regularly arranged 

 bacilli. 



In the sputum, as, indeed, in tubercular tissues, the 

 bacillus may be entirely extra-cellular, or may occur 

 singly, or in groups within the polynuclear pus cells. 

 In Fig. 25 the great majority of the organisms lie 

 without the cells whose nuclei are scattered over the 

 field. 



In Fig. 27, on the contrary, the bacilli are formed 

 almost exclusively within the cells, many of which 

 contain large groups of the micro-organism, and in 

 some of these groups the parallel arrangement of 

 the bacilli occurs. 



It will be observed that in the specimens 25-28, 

 two of which are preparations from sputum and 

 one from the material found in a small tubercular 

 cavity, there are practically no extraneous organisms. 

 This, of course, is not always the case, and secondary 

 infections play an important part in the processes of 

 excavation ; but, speaking broadly, those portions of 

 fresh sputum which contain many tubercle bacilli do 

 not contain very many other microbes, though in 

 neighbouring portions many varieties of organisms 

 may be found. 



When found in the urine (Fig. 30) from cases 

 of tuberculosis of the urinary tract, the bacillus 



