Welcome to the PPRL © PERIODIC PARALYSIS RESEARCH LIBRARY The information provided on this site is designed to support not replace the relationship that exists between a patientsite visitor and hisher existing physician. To emphasize the value of studying human variants Sir Archibald Garrod 1909 quoted a letter written by William Harvey in 1657 Nature is nowhere accustomed more openly to display her secret mysteries than in cases where she shows traces of her workings apart from the beaten path nor is there any better way to advance the proper practice of medicine than to give our minds to the discovery of the usual law of Nature by careful investigation of cases of rarer forms of disease. For it has been found in almost all things that what they contain of use or application is hardly perceived unless we are deprived of them or they become deranged in some way. .