2. Fill in prepositions where necessary.

1. Sometimes intrinsic factors are latent ... the plant and only appear as a response ... the appropriate external factors.

2. Drugs ... general arise ... a heterogeneous population of individual plants living ... a variety of conditions.

3. The inactive principles may alter the activity of the drug ... physi­cal means, ... example, they may act as co-solvents of the active compounds or delay their absorption or diffusion ... the organism.

4. Also the inactive compounds may interfere ... the action of the active... ones or they may be their precursors.

5. The inactive substances include ... cellular structures and pharma­cological inactive ... compounds.

6. Besides their own essential ... principles, the so-called primary plant products, plants produce ... other principles, which appar­ently do not ... have any definite biological function.

7. Medicinal plants are important ... many reasons: they provide us with natural drugs, ... active constituents or ... the intermediates ... semi-synthetic drugs.

3. Complete the sentences using words and phrases from the text.

1. Nature produces an astonishing variety of complex phytoconstituents ... .

2. The inactive compounds may interfere with the action ...

3. The inactive principles may alter the activity of the drug by physi­cal means, for example ....

4. Sometimes intrinsic factors are latent in the plant and only appear as ....

5. Their biological function is often discussed but the fact is that many of them have a special importance outside ....

6. Besides their own essential principles, the so-called primary plant products, plants produce other principles, which ... .

7. Plants are constantly metabolising, both breaking down ....

8. Nature produces an astonishing variety of complex ....

4. Correct mistakes in the following statements.

1. The inactive principles may alter the activity of the drug by physi­cal means, for example, they may act as co-solvents of the non-active compounds.

2. Besides their own essential principles, the so-called primary plant products, plants produce other principles, which apparently have definite biological function.

3. Plants are constantly metabolising, both breaking down preformed molecules and at the same time destroying old ones.

4. Nature produces an astonishing variety of complex phytoconstitu-ents which embrace all fields of pharmacological action.

5. The biological function is often discussed but the fact is that many of them have a special importance inside the plant because of their pharmacological action.

6. Sometimes intrinsic factors are latent in the plant and only appear as a response to the appropriate internal factors.

7. The active compounds may interfere with the action of the active ones or they may be their precursors.

8. Drugs in general arise from a heterogeneous population of indi­vidual plants living under proper conditions.