Some other internal remedies, and many other external applications, have been used in Skin diseases; but these that I have mentioned are the only ones that appear to exert something of a special action in all cases. Arsenic is perhaps the most universal in its application. It often happens that when this remedy entirely fails, the eruption is connected with a constitutional taint of Syphilis. When there is a suspicion of this, such a remedy as Donovan's solution, containing both Arsenic and Mercury, is peculiarly applicable, because capable of acting in a double way. This medicine also contains Iodine; and either this preparation, or the Iodide of Potassium, should be prescribed when the skin disease appears to be connected with a strumous diathesis.
As soon as the course of Arsenic is found to produce swelling of the face, or irritation of the conjunctivæ, symptoms which denote the saturation of the system with the remedy, its administration should be suspended for a while.
We have now concluded the subject of Hæmatic medicines. I have said that this class has been very generally neglected and overlooked by writers on the subject. For this reason, and because there are some ideas respecting their action which I have thought it worth while to work out and to investigate at some length, I have devoted more space to its elaboration than I shall be able to spare for either of the remaining classes, in the consideration of which we are not likely to encounter so many interesting and debateable points.
PROP. VIII.--_That a second class of medicines, called_ NEUROTICS, _act by passing from the blood to the nerves or nerve-centres, which they influence._
1. _That of these, some, called_ STIMULANTS, _act so as to exalt nervous force in general or in particular._
2. _That others, called_ NARCOTICS, _act so as first to exalt nervous force, and then to depress it; and have also a special influence on the intellectual part of the brain._
3. _That others again, called_ SEDATIVES, _act so as to depress nervous force, in general or in particular._
Having investigated at some length the action of Blood-medicines, we now commence the consideration of another class of remedies, which differ very widely from the last in their mode of operation.