The second of these objects has been achieved by the researches of Ehrlich, who, in conjunction with his pupil, Hata, has built up a compound, the dihydrochloride of dioxydiamido-arseno-benzol, popularly known as salvarsan or “606.”  Other preparations, such as kharsivan, arseno-billon, and diarsenol, are chemically equivalent to salvarsan, containing from 27 to 31 per cent. of arsenic, and are equally efficient.  The full dose is 0.6 grm.  All these members of the “606” group form an acid solution when dissolved in water, and must be rendered alkaline before being injected.  As subcutaneous and intra-muscular injections cause considerable pain, and may cause sloughing of the tissues, “606” preparations must be injected intravenously.  Ehrlich has devised a preparation—­neo-salvarsan, or “914,” which is more easily prepared and forms a neutral solution.  It contains from 18 to 20 per cent. of arsenic.  Neo-kharsivan, novo-arseno-billon, and neo-diarsenol belong to the “914” group, the full dosage of which is 0.9 grm.  As subcutaneous and intra-muscular injections of the “914” group are not painful, and even more efficient than intravenous injections, the administration is simpler.

Galyl, luargol, and other preparations act in the same way as the “606” and “914” groups.

The “606” preparations may be introduced into the veins by injection or by means of an apparatus which allows the solution to flow in by gravity.  The left median basilic vein is selected, and a platino-iridium needle with a short point and a bore larger than that of the ordinary hypodermic syringe is used.  The needle is passed for a few millimetres along the vein, and the solution is then slowly introduced; before withdrawing the needle some saline is run in to diminish the risk of thrombosis.

The “914” preparations may be injected either into the subcutaneous tissue of the buttock or into the substance of the gluteus muscle.  The part is then massaged for a few minutes, and the massage is repeated daily for a few days.

No hard-and-fast rules can be laid down as to what constitutes a complete course of treatment.  Harrison recommends as a minimum course of one of the “914” preparations in early primary cases an initial dose of 0.45 grm. given intra-muscularly or into the deep subcutaneous tissue; the same dose a week later; 0.6 grm. the following week; then miss a week and give 9.6 grms. on two successive weeks; then miss two weeks and give 0.6 grm. on two more successive weeks.

When a positive Wassermann reaction is present before treatment is commenced, the above course is prolonged as follows:  for three weeks is given a course of potassium iodide, after which four more weekly injections of 0.6 grm. of “914” are given.

With each injection of “914” after the first, throughout the whole course 1 grain of mercury is injected intra-muscularly.

In the course of a few hours, there is usually some indisposition, with a feeling of chilliness and slight rise of temperature; these symptoms pass off within twenty-four hours, and in a few days there is a decided improvement of health.  Three or four days after an intra-muscular injection there may be pain and stiffness in the gluteal region.