Humans are the only animals definitely known to shed emotiomal tears. Since evolution has given rise to few, if any, purposeless physiological responset, it is logical to assume that crying has one or more functions that enhance survival.
Although some observers have suggested that crying is a way to clicit assistance form others , the shedding of tears is hardly necessary to get help. Vocal cries would have been quite enough, more likely than tears to gain attention, So, it appears, there must be something special about tears themselves.
Indeed, the new studies suggest that emotional tears may play a direct role in alleviating stress, University of Minnesota researchers who are studying the chemical composition of tears have recently isolated two important chemicals from emotional tears. Both chemicals are found only in tears that are shed in response to cmotion. Tears shed because of exposure to =cut onion would contain no such substance.
Researchers at several other institutions are investigating the usefulness of tears as a means of diagnosing human ills and monitoring drugs.
At Tulane Universitys Teat Analysis Laboratory Dr.Peter Kastl and his colleagues report that they can use tears to detect drug abuse and exposure to medication, to determine whether a contact lens fits properly of why it may be uncomfortable, to study the causes of dry eye syndrome and the effects of eye surgery, and perhaps even to measure exposure to environmental pollutants.
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