1. Furthermore, immune responses to tubercle bacilli are extraordinarily complicated.

2. Koch identified the tubercle bacillus only in 1882.

3. They are plants of the most varied appearance, and they also possess either a bulb or tubercle.

4. After the tubercle bacillus was identified, accurate diagnosis of tuberculosis, of the lungs and of other organs, became possible.

5. On the roots oblong tubercles which are obviously reserve organs are formed.

6. The growth of the plants from tubercles treated in this manner is then very fast.

7. We are not likely to find a cause as precisely as the tubercle bacillus can be shown to produce tuberculosis.

8. For this purpose only those plants obtained from well developed tubercles are used.

9. So the tubercle bacillus is a particularly difficult target for chemical attack.