1.   It is thought that the head secretes a substance which is capable of breaking down the outer layer of the ovum.

2.   The pancreas secretes a substance called insulin.

3.   Among lumbricids, the familiar band of tissue encircling the worm behind its head secretes a substance that hardens into a ring-shaped cocoon.

4.   For instance, the ovaries secrete other substances besides estrogen that might affect aging.

5.   Folkman has shown that primary tumors can secrete antiangiogenic substances that keep secondary cancer growths from spreading.

6.   On the one hand, they had found substances secreted by white blood cells that seemed to stop the AIDS virus in its tracks.

7.   The immune cells also secrete substances called cytokines that lead to inflammation, attracting more immune cells.

8.   The term refers to the process by which the body secretes substances that lead to the sprouting of the new blood vessels that are needed for tumor growth.