| MadSci Network: Anatomy |
In live animals, fat is living tissue (generally called adipose tissue). The fat exists as stored lipid in organelles within cells that exist primarily for that purpose. On a gross (large-scale) level, it can appear yellow and greasy, but histologically, fat is a well-organized tissue. Blood vessels, lymph channels, and other connective tissue elements exist between the fat storage cells in the tissue.
Pus is not a tissue. It is typically just the debris left over from a localized inflammatory process, most often associated with bacterial infection. Very little of it is living cells, and what living cells are within (whether they be host immune cells or the invading organisms that they're fighting) are not well organized. Pus does not act as a means for storing calories as fat does. Pus does not contain a high proportion of lipid, so that biochemically it is *quite* different from fat. Pus can appear yellow and moist as fat does on a gross (in both senses of the word) level, but adipose tissue in living tissue is solid, whereas pus in living tissue is typically liquid.
Fat storage in plants involves much different forms of fat, often fats that are liquid at ambient temperatures, so that we refer to them as oils. I know very little about plant immunity, so I don't know if they make anything resembling pus during their battles with invaders.
Tim Nicholls, MD
Berkeley, CA
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