In the anatomy of the male human body, the bulbourethral glands (or Cowper's glands) are two small, rounded, and somewhat lobulated bodies, of a yellow color, about the size of peas, placed behind and lateral to the membranous portion of the urethra, between the two layers of the fascia of the urogenital diaphragm. They lie close above the bulb, and are enclosed by the transverse fibers of the Sphincter urethrae membranaceae . Their existence is said to be constant: they gradually diminish in size as age advances.
The excretory duct of each gland, nearly 2.5 cm long, passes obliquely forward beneath the mucous membrane, and opens by a minute orifice on the floor of the cavernous portion of the urethra about 2.5 cm in front of the urogenital diaphragm.
They secrete a clear fluid known as pre-ejaculate or Cowper's fluid (colloquially known as "pre-cum") which is generated upon sexual arousal.
Cowper's glands in males are homologous to Bartholin's glands in females.
Structure
Each gland is made up of several lobules, held together by a fibrous investment. Each lobule consists of a number of acini , lined by columnar epithelial cells , opening into one duct, which joins with the ducts of other lobules outside the gland to form the single excretory duct.
Note: The first version of this article was taken from the public domain text of the 1918 edition of Gray's Anatomy, and so may not reflect modern anatomical knowledge -- please update as necessary