478 | ANNUAL REPORT SMITHSONIAN INSTITUTION, 1944 
fundamental concepts concerning reactions of the host to the infectious 
agent must be clarified. Perhaps the most important of these concepts 
is the relation between the hypersensitive or allergic response and im- 
munity.” Shall we immunize our children against tuberculosis? We 
immunize them against diphtheria; why not against tuberculosis? In 
1940, 60,428 persons died of tuberculosis in the United States and only 
1,457 of diphtheria. It may be objected that tuberculosis is not a child- 
hood disease. It is not, and it is much less so now than it was in 1900, 
but in 1940 a total of 2,787 children under 15 years of age died of 
tuberculosis, almost twice the total number dying of diphtheria. 
When we have clinical tuberculosis where do we get it? Is it from 
within—the lighting up of an old arrested focus—or is it from without 
by contact, often repeated, with open cases of tuberculosis? We now 
favor the latter view, exogenous infection, but it has not been many 
years since the former view, endogenous infection, was our gospel. 
Years ago we used to speak of the childhood type of tuberculosis. Now 
we call it “first infection phase.” In this form of infection the tubercle 
bacillus localizes in the outer parenchyma of the lower- or mid-lung 
field, and there is developed an area which, when it later becomes en- 
capsulated, calcified, or perhaps even ossified, is known as a Ghon 
tubercle. Before this happens, however, the little colony of tubercle 
bacilli, often too small to be seen with the naked eye, establishes con- 
nection with functionally adjacent lymph nodes and there sets up a 
focus of tuberculous infection that in time usually becomes calcified 
and, if large enough, visible in X-ray plates. The tubercle and its 
involved lymph node form the Complex of Ranke. As a usual thing 
an individual harboring this pathology suffers, particularly if he is not 
a very young or a weakly person, few if any clinical symptoms. Some 
years ago it was believed that almost every child had such a “primary 
infection.” Now it is known that most children escape any form of 
tuberculous infection and that “first infection phase” tuberculosis 
comes in both adults and children. Is it the same usually benign 
disease in adults that it used to be in children, or is it much more seri- 
ous? We have a debatable proposition. 
Years ago we used to speak also of the “adult” form of tuberculosis. 
Now we call it “reinfection phase” tuberculosis. This is tuberculosis 
developing in an individual who has had “first infection phase” tuber- 
culosis and is thereby a different host from the individual never con- 
tacted successfully by the tubercle bacillus. In this form of disease 
the lesion usually appears in the upper third of the lung and does not 
involve the functionally connected lymph nodes. When such lesions 
heal they show less of calcification and more of resorption and fibrosis. 
Spread of this type of disease, which frequently occurs, is by caseation, 
liquefaction, and excavation. This “adult” type of disease can, of 
