Benzol (benzene, C6H6) is a colorless, inflammable liquid, insoluble in water, soluble in 4 parts of alcohol, and freely miscible with the oils. It is a solvent for phenol, a property by which it can be differentiated from benzine. Sellings (1910) reported 7 cases of purpura hemorrhagica in tin workers who used a benzol preparation as a substitute for solder. Santesson (1897) and also McClure (1916) reported series of cases of aplastic anemia from the use of benzol as a solvent for rubber. Following Sellings work v. Koranyi applied benzol to the treatment of leukemia.

In experimental work on rabbits by Sellings and others, there has been noted a primary rise in the leukocyte count followed by an irregular fall, after which there may be a secondary rise and a secondary fall, and finally a return to normal when the drug is stopped. The blood-forming tissues, the bone-marrow, spleen, lymph-nodes, and lymph-follicles are rendered aplastic, and may become atrophic. The result is an aplastic anemia with diminution in the number of blcod-platelets and white cells, the poly-nuclear count being relatively more affected than the mononuclear. The liver and kidneys show fatty changes, and in some animals there are hemorrhages into the wall of the stomach and intestines and into the lungs. After stopping the benzol, Sellings found complete regeneration of the aplastic organs in ten to twenty-one days.

The red blood-cells may be increased primarily, but they soon show the effects of the bone-marrow aplasia in a progressive anemia, with hemoglobin index about 1 and pratical absence of nucleated red cells. Musser and Krumbhaar in 6 rabbits could not produce purpura, though they obtained the characteristic anemia and leukopenia. With the use of benzol there is an increase in the phenols of the urine.

Benzol is not a cure for leukemia, but may be looked upon as a symptomatic remedy. There are wide differences in individual tolerance to the drug, so that the dose is uncertain. The beginning dose, however, may be put at 8 minims (0.5 c.c.) three times a day, and this amount is rapidly increased to double. It may be given after meals in milk, or in capsules with equal parts of olive oil. Mixed with olive oil it has also been used subcutaneously and by rectum, but it is irritant. Winslow and Edwards (1917) gave it intravenously to dogs and rabbits, with immediate agitation, convulsions, and if the dose were large enough, death. The lethal dose for 2 dogs weighing 25 and 29 pounds was 45 minims (3 c.c.). In man it must not be employed intravenously. If the leukocytes show a rapid fall in number, the benzol should be stopped no matter how high the count, for this is an indication of severe aplasia. The author had one case (demonstrated by Dr. J. H. Larkin at the New York Pathological Society) with over 1,000,000 white cells per cubic millimeter. The benzol, 45 minims (3 c.c.) daily, was stopped when the leukocytes fell rapidly to about 200,000, but rapid progress downward continued, and when the count reached 10,000 the patient died. The bone-marrow was very red, and showed crowded myelocytes with much new connective tissue, new vessels, and hemorrhages. Billings and others have noted basophilic granular degeneration of the lymphocytes. In the two fatal poisoning cases of Sellings series the leukocytes fell to 480 and 140 per cubic millimeter. From the use of the drug in leukemia Neumann reports a drop of white cells to 200. Other untoward effects from its medicinal use are heart-burn, flatulence, nausea, vomiting, diarrhea, bronchial irritation, minute hemorrhages of skin and mucous membranes (purpura hemorrhagica), albuminuria, ringing in the ears, and dizziness.

In addition to lymphoid and myeloid leukemia, benzol has been recommended in pseudoleukemia and polycythemia. Ki-ralyfi reports no effect in Banti's disease, and the most marked effect in lymphoid leukemia. Others have noted the best effects in myeloid leukemia, and Sellings found experimentally that the myeloid tissues were most affected. In the severe aplastic anemia of benzol poisoning McClure obtained recovery in one case by repeated transfusions of blood to the number of five.