Having done this, we may afterwards try, if we can, to invent for this action a theoretical explanation. Our arguments and theories will not affect the fact, nor will they lead us into danger, if we have first laid down the truth, however incomprehensible, as the only secure foundation, in such a manner that it shall be incapable of being disturbed by the flimsy superstructure. Some philosophers have erred in this; that they have first, with much pains and labour, erected an airy fabric on a basis of incontestable truth,--but subsequently, relying too much on that which they have themselves raised, they have commenced to pull up the blocks on which it was founded, and have thus brought the whole speculation tumbling to the ground in ruins. Considering then that the action of Catalytic medicines in each disorder is of a special and peculiar kind, which I think will not be denied, I have grouped them in orders which are named according to the several morbid states in which they are employed. CATALYTICA. Ord. 1. Antiphlogistica. Ord. 2. Antisyphilitica. Ord. 3. Antiscrofulosa. Ord. 4. Antiarthritica. Ord. 5. Antiscorbutica. Ord. 6. Antiperiodica. Ord. 7. Anticonvulsiva. Ord. 8. Antisquamosa. The medicines of the first order are employed in inflammatory disorders generally, and possess an influence over the process of sthenic inflammation, however first produced. The second order contains those that are used in the several forms of Syphilis. The third, those that are employed in Scrofula. The fourth, those that are found to be useful in the cure of painful affections of the joints, as Gout and Rheumatism; and also of Oxaluria, Lithiasis, Diabetes, and other disorders of secondary assimilation. The fifth order contains those that are useful in Scurvy. The sixth, those that are employed in Ague, Remittents, and other periodic disorders, on the Catalytic principle. The seventh, those used in convulsive disorders. Lastly, the eighth, those that are capable of curing Lepra, Psoriasis vulgaris, and some other skin diseases. The action of these medicines being much more obscure than that of Restoratives, I shall therefore have less to say about them individually, and shall not go so much into particulars. That part of Prop. VII. which refers to Catalytics, may be divided into the following minor propositions:-- _m. p._ 1.--That they act in the blood, and that their effect is permanent. _m. p._ 2.--That each of itself tends to work out a peculiar operation in the blood. _m. p._ 3.--That the diseases in which they are used depend on certain morbid materials or actions in the blood. _m. p._ 4.--That the result of the action of a Catalytic medicine is in some way to neutralize or counteract some one or more of these morbid processes.