258 BACTERIOLOGY. 



detritus, it is rare that the organisms can be demon- 

 strated microscopically. It is at the periphery of these 

 areas and in the progressing granular zone that they are 

 most frequently to be seen. 



This apparent absence of the bacilli from the central 

 necrotic area must not be taken, however, as evidence 

 that this tissue does not contain them. As bacilli, they 

 are difficult to demonstrate here because the probabili- 

 ties are that in this locality, owing to conditions unfa- 

 vorable to their further growth, they are in the spore 

 stage, a stage in which it is as yet impossible, with our 

 present methods of staining, to render them visible. 

 The fact that this tissue is infective, and with it the 

 disease can be reproduced in susceptible animals, speaks 

 for the accuracy of this assumption. A conspicuous 

 example of this condition is seen in old scrofulous 

 glands. These glands usually present a slow process, 

 are commonly caseous, and always possess the property 

 of producing the disease when introduced into the tis- 

 sues of susceptible animals, and yet they are the most 

 difficult of all tissues in which to demonstrate micro- 

 scopically the presence of tubercle bacilli. 



In tubercles containing giant-cells the bacilli can 

 usually be demonstrated in the granular contents of 

 these cells. Frequently they will be found accumu- 

 lated at the pole of the cell opposite to that occupied 

 by the nuclei, as if there existed an antagonism between 

 the nuclei and the bacilli. In some of these cells, 

 however, the distribution of the bacilli is seen to be 

 irregular, and they will be found scattered among the 

 nuclei as well as In the necrotic centre of the cell. As 

 the number of bacilli in the giant-cell increases the 

 cell itself is ultimately destroyed. 



