<Li> Functio laesa (loss of function) </Li> <P> The first four (classical signs) were described by Celsus (ca . 30 BC--38 AD), while loss of function was added later by Galen even though the attribution is disputed and the origination of the fifth sign has also been ascribed to Thomas Sydenham and Virchow . </P> <P> Redness and heat are due to increased blood flow at body core temperature to the inflamed site; swelling is caused by accumulation of fluid; pain is due to the release of chemicals such as bradykinin and histamine that stimulate nerve endings . Loss of function has multiple causes . </P> <P> Acute inflammation of the lung (usually caused in response to pneumonia) does not cause pain unless the inflammation involves the parietal pleura, which does have pain - sensitive nerve endings . </P>

What is the first step in the major events of the inflammatory process