History
Sick animals have long been recognized by farmers as having different behavior. Initially it was thought that this was due to physical weakness that resulted from diverting energy to the body processes needed to fight infection. However, in the 1960s, it was shown that animals produced a blood-carried ‘‘factor X’’ that acted upon the brain to cause sickness behavior. In 1987, Benjamin L. Hart brought together a variety of research findings that argued for them being survival adaptations that if prevented would disadvantage an animal’s ability to fight infection. In the 1980s, the blood borne factor was shown to be proinflammatory cytokines produced by activated leukocytes in the immune system in response to lipopolysaccharides (a cell wall component of Gram-negative bacteria). These cytokines acted by various humoral and nerve routes upon the hypothalamus and other areas of the brain. Further research showed that the brain can also learn to control the various components of sickness behavior independently of immune activation.
Read more about this topic: Sickness Behavior
Famous quotes containing the word history:
“The greatest honor history can bestow is that of peacemaker.”
—Richard M. Nixon (1913–1995)
“In history the great moment is, when the savage is just ceasing to be a savage, with all his hairy Pelasgic strength directed on his opening sense of beauty;—and you have Pericles and Phidias,—and not yet passed over into the Corinthian civility. Everything good in nature and in the world is in that moment of transition, when the swarthy juices still flow plentifully from nature, but their astrigency or acridity is got out by ethics and humanity.”
—Ralph Waldo Emerson (1803–1882)
“The only history is a mere question of one’s struggle inside oneself. But that is the joy of it. One need neither discover Americas nor conquer nations, and yet one has as great a work as Columbus or Alexander, to do.”
—D.H. (David Herbert)