30 



tubercle bacillus finds a congenial home in which it spreads 

 and thrives and multiplies. 



Again, the condition often seen in some parts antecedent to the 

 formation of tubercles in the human system indicates that there is 

 often some structural change before the bacilli take possession of 

 the part, and " that their appearance on the scene is subsequent to 

 the damage of which they are in fact the pathological conse- 

 quences." Not infrequently, in cases of acute tuberculosis of 

 other organs we find an affection of the membranes of the brain 

 presenting all the characters of simple inflammation, no tubercles 

 being discoverable. And iu the lungs the first stage of the 

 morbid process is of a similar character, namely the filling of 

 the alveoli with epithelial cells, or in other words a "catarrhal 

 pneumonia." And according to the vitality of these epithelial 

 cells will be the changes produced in them by the bacilli. Some 

 of the cells possessing greater vitality will, when attacked by 

 the bacilli, go on increasing or coalescing, and so, in some way 

 or other, the formation of the so-called ** giant cells " takes place, 

 which at one time were regarded as the typical elements of 

 tubercle, and the remarkable phagocyte property of which has 

 been recently shown by Metschnikoff to be something more than 

 a theory. If the cells are of a weaker nature they quickly die 

 and undergo degeneration, and become caseous. 



And, once again, it may be suggested that when the bacilli 

 have gained a footing in this effete or enfeebled tissue, whilst 

 absorbing from it the constituents of their own protoplasm, 

 they may give rise to, or secrete, poisonous products or ferments, 

 capable of still further destroying or weakening the surrounding 

 tissue or cellular elements and so obtain fresh food on which 

 they can thrive. In this way, to use Dr Sanderson's words : 



