That the blood may be loaded with a multitude of cells, exactly resembling those of pus that such blood may circulate in the human subject for months, or even years, without destruction to life, and that this condition is always associated with disease in those organs…." So mused English physician and pathologist, Dr. John Hughes Bennett (1812-1875) in his 1852 review "On Leucocythemia, or Blood Containing an Unusual Number of Colourless Corpuscles." 1 Widely credited with first describing leukemia as a blood-related disease, which he termed leucocythemiafrom λευκóς (white), κy τος (cell), and αίμα (blood), literally white cell blood-Bennett hypothesized that an excess of leucocytes in the absence of infection or inflammation was due to a primary systemic blood disorder.John Menteith, a young 28-year-old Scottish male slater, was Bennett's index case of leucocythemia. On February 27, 1845, Menteith was admitted to the Royal Infirmary of Edinburgh under the care of Dr. Robert Christison (1797-1882. Menteith suffered from a chronic, progressively enlarging left hypochondrial tumor and generalized lymphadenopathy. Significant diarrhea on March 10 was treated with a combination of castor oil and opium pills. Fever on March 13 was medicated with tinctures of ammonia, morphine solution, spring water, and a quarter ounce of syrup every hour. This was followed by Menteith's sudden demise on March 15. Bennett, performing the autopsy 4 days later, discovered massive hepatosplenomegaly, extensive lymphadenopathy, and blood clots within the blood vessels. Light microscopy of