Light micrograph (LM) of an active human mammary gland. A mammary gland is an exocrine gland in mammals that produces milk to feed young offspring. The mammary glands are arranged in organs such as the breasts in primates, the udder in ruminants, and the dugs of other animals. A mammary gland is a specific type of apocrine gland specialized for manufacture of colostrum when giving birth. Mammary glands can be identified as apocrine because they exhibit striking decapitation secretion. Magnification: 40x at 35mm.