Dr. Universe, an informational website project of Washington State University, published the following description of pus (accessed Feb. 1, 2008):
"Pus is made up mostly of a special kind of white blood cell called NEUTROPHILS. Their main job is to eat and digest invading microorganisms such as bacteria. In the process of fighting off infection, they die. So pus is a battleground full of soldiers, living and dead. It also contains bacteria and dead cells from the surrounding tissue."
Food Production Daily, an online food producer's news service, wrote in its Mar. 10, 2002 article "PETA [People for the Ethical Treatment of Animals] launches 'Got Pus?' campaign," published on the Food Production Daily website:
"Somatic cells are white cells [leukocytes] that are present in both humans and cows, said David Reid, a dairy veterinarian in Hazel Green. While white blood cells are present in pus, they do not constitute pus in and of themselves. At proper levels, somatic cells prevent cows from getting mastitis, Reid said. High levels of somatic cells in milk indicate that a cow is sick and should not be milked until it is treated, he added."
Jeffrey W. Hull, MD, FAAP, practicing pediatrician, provided the following definition of pus in his online resource "Parents' Common Sense Encyclopedia," posted on his website (accessed Dec. 19, 2007):
"Pus is formed by the collection of large numbers of white cells [leukocytes] called polymorphonuclear cells in a localized area of the body in response to the presence of bacterial infection.
These cells break down and release chemicals that kill the bacteria as well as cause enlargement of the blood vessels (inflammation) and attract more white cells to the 'fight.'...
Polymorphonuclear cells are of three types: neutrophils, eosinophils, and basophils. Neutrophils fight bacterial infection. They form pus and are the chief ingredient of an abscess."
Chart of the Different Types of White Blood Cells (Leukocytes)