TUBERCULOSIS. 231 



bacilli in the healthy individual, and in a minor degree 

 even in individuals with weaker tissues ; the activity of the 

 bacilli is so interfered with or modified that they can be 

 readily attacked and devoured by the tissue cells, which, as has 

 long been known, have a most remarkable power of taking 

 up into their substance many effete materials and particles 

 of dead or inorganic matter. On the other hand, certain 

 excretions, by accumulating in the blood and in the lymph 

 spaces, may impair the activity of these tissue cells and so 

 render them less able (i) to secrete their protective material, 

 and (2) to wage war directly against the bacilli ; whilst, in 

 turn, the bacilli on their side, as we have already seen, secrete 

 a material that has a most injurious action on the tissue 

 cells, causing them to swell up and eventually to become 

 hyaline. This material is only a poison when in large or 

 comparatively large quantities ; in smaller doses it acts 

 in the first instance as an irritant or stimulant, stimula- 

 ting the protoplasm to exert all its powers against the 

 advancing bacteria, powers that are so strongly exerted (un- 

 less the conditions of nutrition and excretion are specially 

 favourable) that they are rapidly exhausted. It has been 

 observed that in those cases where phthisis was curable the 

 cure has been effected only by careful nutrition of the 

 tissues, and that as soon as they have been brought up to 

 a certain standard of health the disease has been checked, in 

 many cases permanently ; on the other hand it has been 

 found that when the tissues have again fallen below par there 

 has been a fresh outbreak of the disease. These facts are in 

 themselves sufficiently interesting and suggestive, but as we 

 shall see they have a further important bearing on the 

 question of the curability of the tubercular phthisis. 



It has been observed that a process of localization occurs 

 even when large caseous patches have been formed, and it 

 has been found that around these patches, just as around an 

 abscess, there is always erected a kind of barrier, made up 

 of vigorous connective tissue cells, small, round and larger 

 epithelioid cells ; the blood vessels in this cellular zone 

 being comparatively numerous and of considerable size. We 

 have, in fact, in this arrangement of the blood vessels and 

 cells, a making of roads (the blood vessels) for the bringing 

 up and massing of forces (the active cells) around the 

 enemies' camp (the tubercular or caseous mass with the con- 



