PRACTICAL APPLICATIONS 377 



truly a local one ; meaning thereby that in pure tuberculosis the 

 general symptoms indicative of a spread of the toxins into the 

 general circulation are but slight, and the local lesion constitutes 

 almost the whole of the disease. Note, for instance, the good 

 general health which often occurs in patients with tuberculous 

 glands in the neck, even if of some size. And where the general 

 health is impaired, it will often be found to be a predisposing 

 cause rather than a result of the tuberculous process. 



Immunity. These facts would tend to show, what I believe to 

 be the case, that the immunity to tubercle is local rather than 

 general. That general immunity exists there can be no doubt, 

 but we must distinguish between general immunity due to a 

 condition of the blood and that due to a resisting power inherent 

 in all the tissues of the body. Thus to take two patients, one 

 strong and robust and the other of enfeebled vitality : the latter 

 may fall a ready victim to tubercle, whilst the former resists 

 exposure to the most virulent infection : yet there may be no 

 demonstrable difference in the serum of the two persons. There 

 may, it is true, be a slight difference in the opsonic index, but this 

 is not invariably the case. 



The importance of local immunity in tubercle appears clearly 

 from the fact that areas of advance and of cure may occur in the 

 same patient, or even in different parts of the same lesion. This 

 is often very well seen in cases of lupus, but is even more 

 marked in sections from chronic tuberculosis^.^., of a synovial 

 membrane, in which areas of cure (as indicated by fibrosis and 

 organization of the giant-cell systems) and of extension (as in- 

 dicated by caseation and the formation of new tubercles) may 

 almost always be found in the same lesion. In general, tubercle 

 tends to spontaneous cure, and when a lesion continues to spread 

 it will often be found that some second influence (such as a 

 secondary infection) is at work ; even in debilitated subjects there 

 is usually an effort at spontaneous cure in some parts of the 

 lesion. 



As regards the nature of this process of cure, we can say but 

 little. There can be but little doubt that the main curative 

 agency is phagocytosis, but there is no reason to think that this 

 is dependent on the same mechanism of opsonic action that we 

 reproduce so readily in vitro. Poly nuclear leucocytes are con- 

 spicuous by their absence from tubercles, and the only cells in 

 which tubercle bacilli have actually been demonstrated in the 



