During this time, the female feeds the developing offspring with a milky substance secreted by a modified gland in the uterus.

Adrenin is a substance secreted into the blood by the adrenal glands.

Pheromones are simply chemical substances secreted by an animal which has an effect on the behaviour of a member of its species.

Tectin is an organic substance secreted by certain ciliate protozoans.

Lanolin - a thick yellow greasy substance in wool, secreted by the sheep's skin.

True coral, however, is a hard calcareous substance secreted by marine polyps for habitation.

The oily substance, secreted by your hair follicles, is the body's natural hair conditioner.

Did the heart stop because it was poisoned by some as yet unknown substance secreted by the cancerous cells?