_Catalytic medicines act in the blood, and their effect is permanent._ This is simply to affirm that they belong to the class of Hæmatics, to which Restoratives also belong. Of all that I have named, there are not any, except Colchicum and Antimony, that possess in any degree the action of nerve-medicines--_i.e._ that exert a sudden and transient influence over the nervous system. I believe the sedative powers of these medicines to be quite distinct from their Catalytic influence. In the proof of the second minor proposition, I shall attempt to show that each of these remedies has a peculiar action of its own on the blood, even in health; which cannot be said of Restorative medicines. Of all these Catalytics two things are known. When they cure a disease, they do so definitely, so that it does not in general tend to return; and when they only alleviate it, the improvement effected is more or less permanent. In the second place, they are found to produce, after being long administered, a change for the worse in the blood, a diminution in the amount of Fibrine and of the red corpuscles. Thus they are blood-impoverishers, when given in excess. These considerations alone, when combined with the proof of absorption--_i.e._ that they all pass into the secretions, and may be detected there--are conclusive as to the fact of their being Hæmatic medicines. We pass on now to the third proposition, which consists in the statement of a property that is peculiar to Catalytic Hæmatics. _Each Catalytic tends of itself to work out a peculiar operation in the blood._ This peculiar process, established by their presence in the blood, forms part of the known history of each Catalytic medicine. It will suffice to demonstrate this if I condense into as few words as possible the facts that are known on this subject, with respect to each of the orders of this division of remedies. Of _Antiphlogistic_ medicines, some possess a power which stamps them at once as likely to be useful in the treatment of inflammatory disorders. Alkalies are known to have the chemical property of holding Fibrine in solution. By exerting this power in the blood, it seems that they may prevent its abnormal deposition or coagulation in inflammatory cases, and at length diminish it in quantity. On this principle they were proposed and used successfully by Mascagni in acute inflammations. Their efficacy in retarding the formation of crude deposits in scrofulous and tubercular diseases may possibly be assigned to the same operation. Potash has been extolled by Dr. Theophilus Thompson as a powerful preservative for those who are predisposed to phthisical disease. Alkalies in small doses, and in cases requiring them, may be Restoratives.