It is probable that many of our natural remedies owe their efficacy to the results of a similar species of combination. In the fourth edition of this work it was stated that, according to the assertion of Dr. Chapman, “_Kino_, when administered in union with _Calumba_, constituted a pretty certain, and powerful purgative;” since the publication of this fact, I have investigated what, if true, would appear to be a most extraordinary anomaly in the philosophy of medicinal combination, and I find that the statement of Dr. Chapman[264] is not borne out by experiment. That we might arrive at a just conclusion upon this subject, I requested the assistance of my friend Dr. John Davy, whose character for experimental accuracy, and whose situation as Superintendant of the Medical Division of the General Military Hospital at Chatham, seemed to point him out as a person peculiarly adapted for such an inquiry; the result of his trials does not establish that of the experiments of Dr. Chapman, but on the contrary it seems to prove, that neither _Kino_ nor _Calumba_, when taken separately, has a constipating effect, and that in the form of powder (especially the _Calumba_) each has an aperient quality, which is not increased by exhibiting the two medicines together in a state of mixture. The trials from which these inferences are drawn were made on different individuals in tolerable health, and they were repeated more than once; in some cases they were given separately, and in others, mixed together, in doses varying from a scruple to a drachm of each. B. _By combining Substances which have the property of acting chemically upon each other; the result of which is the formation of_ NEW COMPOUNDS, _or the decomposition of the original Ingredients, and the developement of their more_ ACTIVE ELEMENTS. A. _The Formation of New Compounds._ It is not necessary to extend our researches beyond the range of the Pharmacopœiæ,[265] to collect a variety of interesting and important examples, in illustration of this division of our subject; if we require a striking example of the agency of chemical combination in destroying the identity of the original constituents, and of giving origin to a compound of new powers, it may be exemplified by the well known instance of _Sulphate of Potass_, a substance possessing but a weak affinity for water, and exerting but little energy upon the animal œconomy; whereas the two ingredients of which it consists are distinguished for the extreme eagerness with which they unite with water, and for the caustic activity which they display in their action upon animal matter.