Over the years, many simple folk rules have evolved to forecast future weather. The formulae have been handed down through countless generations by those whose livelihood depended on the elements. The rules may lack a scientific pedigree, but they were based on observation, and through many of them runs a thread of logic well rooted in experience. Take, for example, the rhyme:
Some by a painful elbow, hip or knee
Will shrewdly guess what weather's like to be;
Some by their corns are wondrous weather-wise
And some by biting lice, or fleas or flies.
The first three lines deserve some meteorological respect. It was noted in experiments carried out more than a century ago, for example, that wounded soldiers seemed to suffer more pain in conditions of falling atmospheric pressure and rising temperature and humidity, than they did at other times. This phenomenon has been objectively verified in more recent times in the case of sufferers from arthritis; arthritic volunteers placed in an isolated hospital room where the climatic variables could be controlled were discovered to have much the same experience.
There is also evidence that changing conditions can lead to discomfort in the case of less serious ailments. In normal circumstances, the human skin detects any change taking place in its environment, and sends corresponding signals to the brain. If, however, a patch of skin is scarred, temperature and moisture changes may induce a tension between this fibrous tissue and the healthy skin surrounding it, resulting in a flash of pain. It may be that this is what happens when "a coming storm your shooting corns presage".
But the last line of the little weather rhyme is more difficult to explain with any credibility. But maybe Richard Inwards, a noted student of these matters in the last century, had the answer.
"In general," Inwards wrote, "the senses of men are coarse and dull, and void of energy. Those also who are distracted by a thousand other objects scarcely feel the impression of the air, and if they speak of it to fill a vacuum in their miserable and frivolous conversation, they do so without thinking of its causes or effects. But animals and insects, which retain their natural instincts, which have their organs better constituted and their senses in a more perfect state, unchanged by vicious and depraved habits, perceive sooner, and are more susceptible to, the impressions produced in them by variations in the atmosphere, and sooner exhibit signs of them."
Perhaps this is why the fleas and flies get all excited, and tend to bite us more, when rain is nigh.