This section is from the book "A Practitioner's Handbook Of Materia Medica And Therapeutics", by Thos. S. Blair. Also available from Amazon: A Practitioner's handbook of Materia Medica and Therapeutics.
Belladonna. Recent investigations and the introduction of scopolamin as an anesthetic prompts some chemical considerations regarding belladonna. For more detailed data the writings of F. B. Kilmer more scientifically cover the subject than anything else of recent date. There are two belladonnas in commerce to-day, the true atropa belladonna and Japanese belladonna or scopolia, the latter being used as an adulterant of the first. Therapeutically, they differ somewhat, although atropine is derived from both plants, and it probably makes little difference in the action of the atropine whether it is made from one or the other plant. There has been much controversy over the chemical educts of these plants, but it appears that hyoscyamine is the principal alkaloid of belladonna, but in the process of separation it is converted into atropine. As to scopolia, it yields more atropine than does belladonna and by the same process. It appears that hyoscyamine of belladonna and scopolamin of scopolia are very similar. We know that atropine, hyoscyamine, and hyoscine have the same formula (C17H13N03), but differ in the graphic formulae owing to varying arrangements of the atoms component of the various alkaloids. The practical points at issue are that belladonna and its educts are to be considered separately in therapeutic action. Prof. Frank Woodbury holds that atropine does not act upon the skin when locally applied as does belladonna, and it is recorded that a small amount of an atropine ointment applied to the unbroken skin has produced death in two hours. Mr. Kilmer says: "Observations made in our laboratory coupled with clinical observations made at our request, and reports from competent observers, have led us to emphatically believe that atropine does not represent the therapeutic value of belladonna." We will first consider the alkaloids and include scopo-lamin, since scopolia will not receive separate consideration in this volume. It appears to be a connecting link botanically between hyoscyamus and atropa belladonna, and presents no defined advantages over these drugs.