EPIDEMIOLOGY OF TUBERCULOSIS—PARR 493 
formerly. This is susceptible to three interpretations. The tubercle 
bacilli in the environment are becoming fewer; they are losing in- 
vasiveness and virulence; or, thirdly, the resistance of the young white 
American to tuberculosis is increasing. The first point is obvious 
but can hardly be the whole explanation. I believe we miss the full 
significance of the data if we do not also allocate some importance 
to each of the other two explanations. 
Weight is added to this suggestion when we consider that the total 
number of tuberculin-negative students in the school, all presumably 
susceptible to successful invasion by the tubercle bacillus, is increasing. 
This number is the census made up each semester after the tests are’ 
done. In November 1941 there were 147 tuberculin-negative students 
in the school. In June 1942 this number was 157. In November 1943 
it was 166 among 313 students, or a student body only 46.9 percent 
tuberculin positive. There has been a slight increase in the total 
number of students in the school, but this has been balanced off by the 
fact that our last two classes, though the initial tuberculin-positive 
rate was low, had higher percentages than the average of the preceding 
four classes (48.3 as against 41.3 percent). Furthermore, since this 
program was started in 1939, only nine students have been found with 
minimal tuberculosis, although three others were detected shortly 
following graduation. At the present time, with 313 students in 
attendance, not one has minimal tuberculosis. This fine record sur- 
passes that revealed in almost any mass survey of adults. Among 
28,098 United States Government employees recently surveyed, 1.1 
percent had recognizable tuberculosis (60.7 percent minimal; 35.3 
percent moderately advanced; 4.0 percent far advanced). 
It has been our purpose in presenting these observations to empha- 
size that, although remarkable progress has been made in combating 
tuberculosis, that progress has not equaled advance achieved in con- 
trolling other well-known diseases. We must believe that tuberculosis 
is still a major problem. Its eradication may be set back by the war 
but not irrevocably. Tuberculosis morbidity and mortality can be 
reduced to a satisfactorily low level, but I do not expect to see in my 
lifetime, the absolute elimination of the disease. Our evidence sug- 
gests that the tuberculosis problem is not at present unduly significant 
for medical students and that there is some ground for considering 
either that the young white adult has more resistance to the tubercle 
bacillus than his father possessed or that the Mycobacterium tubercu- 
losis is losing some of its virulence. Possibly a little of both is true. 
REFERENCES 
ALTSHUEER, S. S., and BAILey, L. J. 
1941. Control of tuberculosis in an institution for the mentally ill. Amer. 
Rey. Tuberc., vol. 44, pp. 335-345. 
