Manipulate and Revitalize..

A good, real, unrestrained, hearty laugh is a sort of glorified internal massage, performed rapidly and automatically.  It manipulates and revitalizes corners and unexplored crannies of the system that are unresponsive to most other exercise methods.  

~Author unknown, from an editorial in New-York Tribune, quoted in Quotations for Special Occasions by Maud van Buren