Before I proceed to any farther discussion upon the present subject, it will be necessary to offer a synoptical view of an arrangement of medicinal bodies founded upon the basis of their operations, in order that I may be better enabled to illustrate the observations which it is my intention to introduce: for this purpose I shall present the reader with three different classifications of this kind; the first being that proposed by Dr. Cullen,[134] and which is now admitted to rest on principles nearly altogether false, but the investigation of which will afford many useful lessons of practical importance; the second classification is by Dr. Young;[135] and the third is that proposed by Dr. Murray,[136] which, from its simplicity and strict conformity with the views I intend to offer, will be adopted as being the most eligible for the occasion. CULLEN’S ARRANGEMENT OF THE MATERIA MEDICA. Medicamenta agunt in SOLIDA. │SIMPLICIA. „ │ _Astringentia._ „ │ _Tonica._ „ │ _Emollientia._ „ │ _Erodentia._ „ │ „ │VIVA. „ │ _Stimulantia._ „ │ _Sedantia._ „ │ _Narcotica._ „ │ _Refrigerantia._ „ │ _Antispasmodica._ FLUIDA. │IMMUTANTIA. „ │ Fluiditatem. „ │ _Attenuantia._ „ │ _Inspissantia._ „ │ Misturam. „ │ Acrimoniam Corrigentia. „ │ _In Genere._ „ │ _Demulcentia._ „ │ _In Specie._ „ │ _Ant-acida._ „ │ _Ant-alkalina._ „ │ _Antiseptica._ „ │ „ │EVACUANTIA. „ │ _Errhina._ „ │ _Sialogoga._ „ │ _Expectorantia._ „ │ _Emetica._ „ │ _Cathartica._ „ │ _Diuretica._ „ │ _Diaphoretica._ „ │ _Menagoga._ CLASSIFICATION OF THE MATERIA MEDICA BY DR. YOUNG. I. CHEMICAL AGENTS. │1. _Caustics._ │2. _Antiseptics._ │3. _Antidotes._ │4. _Demulcents._ │5. _Diluents._ II. VITAL AGENTS. _A._ SUPPORTING STRENGTH. │1. _Nutrients._