On the other hand it is possible from analogy with other infectious diseases that those who are once cured become permanently exempt. This must also be considered an open question for the present. [4] It was impossible to collect data referring to cerebral-laryngeal-and miliary-tuberculosis, as we did not have sufficient material. Explanatory Notes. Koch states that he can not at the present make any statement about the origin and preparation of the remedy, as his labors are not yet completed. We may assume that it is very probably a substance that corresponds in a way to the lymph used for vaccination. As vaccine lymph represents variolous poison greatly reduced in strength, as the remedy for hydrophobia is composed of a substance which is weakened hydrophobic poison, so Koch probably obtains his remedy for tuberculosis by artificially reducing the tuberculous poison by means of various processes. A number of years ago it has been tried with syphilis in a similar way to obtain a substance that would not only cure syphilis but would also guard against infection from it. At that time however the experiment was not successful. From several intimations I am inclined to believe that Koch was successful in finding a way in which a substance may be produced for contagious diseases, a substance that cures these diseases and also protects from infection. It is not impossible, since Jenner found the vaccine virus, Pasteur the hydrophobic lymph and now Koch the tubercle lymph. To be sure there is this difference for the present between the substances named, that the vaccine virus only protects healthy person from infection by small pox but it does not cure those sick, while the hydrophobic lymph and tubercle lymph cure the afflicted. However Koch seems to believe that his tubercle lymph has a certain power of producing immunity. According to Koch, his remedy, consisting of a brownish liquid, is easily perishable as soon as it is diluted with water; he recommends the preparation of the dilution of the remedy with a 5 per cent. phenol solution. Phenol is equivalent to carbolic acid. The dilution of the remedy for use must be considerable, as only small quantities of the same are used. Koch tells us that his remedy does not act through the stomach, that is taken in through the mouth. On one hand it may be that this is due to the extremely small quantities necessary for an effect, on the other hand and principally all the substances probably act only when they are directly applied and brought in contact with the circulation of the blood.