Effect of Ferric Chloride Injections on Spread of Tuberculosis from Site of Subcutaneous Inoculation. ∗

Previous studies have demonstrated that repeated intravenous injections of a 0.25% solution of ferric chloride crystals in tuberculous rabbits are followed by an accumulation of iron in the caseous areas of the lungs.^{1, 2} Subsequent studies revealed that concomitant with this accumulation of iron in tuberculous areas there was a definite increase in the survival time of infected rabbits.^{3, 4} When control and experimental animals were sacrificed at given intervals of time after inoculation with tubercle bacilli, in the majority of instances the extent of the lesion in experimental animals was distinctly less than that found in the controls. 4 The conclusion drawn was that with the accumulation of iron in tuberculous areas, the course of development of the disease is protracted in the rabbit.

Further experiments were set up to determine whether the repeated administration intravenously of ferric chloride solution would retard the dissemination of tubercle bacilli and hence the progress of the disease when microorganisms were inoculated into a subcutaneous area. Prior to the present study inoculation with tubercle bacilli had been performed only by the intravenous route.

A saline suspension of a bovine culture of tubercle bacilli was introduced into the subcutaneous tissue of the abdomen of each of 12 rabbits. Repeated intravenous injections of ferric chloride in concentration of 0.25% were started in 6 of the rabbits, immediately following the inoculation with tubercle bacilli. The remaining 6 tuberculous animals were kept as controls. The method of injecting ferric chloride and the precautions used throughout the course of administration to avoid lethal effects, have been described.^3,4Throughout the period of injections death from embolism was no doubt prevented in the majority of instances by the fact that, as previously pointed out, the precipitate formed by the interaction of 0.25% ferric chloride with blood serum redissolved 5 . As a rule death resulting from intravenous administration failed to occur when the amount of 0.25% ferric chloride injected at one time was below 3 or 5 cc. The injections were always given very slowly.