Today, jewelles and therpists prescribe coloured gemstones to alleviate chronic diseases as well as to effect changes in the life of an individual. Experience has shown that wearing particular gems appears to bring on physical, mental or spiritual relief, and aid one's pursuits in life. However during the Middle Ages, the rise of logic and logical thought altered sensibilities all over Europe. Medicines that removed symptoms of disease immediately were preferred. Traditional practices of healing were dubbed 'wichcraft' and 'sorcery' and so were forced into disuse and to some extent, oblivion. It was an Arab physician, Avicenna who re-invented chromotherapy by prescribing naturally occurring colours to check the spread of disease; the advised patients againts the malevolent effect of unfriendly colours. This method of treatment became popular for a short time during the Renaissance and short into fame in the nineteenth century in America after experiments conducted on plants and animals proved beyond doubt that colours had a strong influence on them. Prison cells were then painted blue to calm their inmates while pink became the prescribed colour for nurseries.