Note 5 — PREFACE.
Reading edition
Dr. Thomson tells me that he has known white precipitate of mercury sold in hundred-weights as calomel, and in one case (he believes by accident or ignorance) as trisnitrate of bismuth. In my text I have endeavoured to adduce such illustrations as I suppose to be most notorious; but I may refer the reader to various interesting papers published, through the last two or three years, in the Lancet (Analytical Sanitary Commission) from one of which I quote the astounding instance, given above, of variations in the strength of laudanum. Mr. Thomas Taylor, of Vere Street, informs me that, whereas an ounce of laudanum should contain about four grains of morphia, he finds the actual quantity varying in different specimens from two grains to six; and that in two specimens of solid opium, outwardly alike and supposed to be of equal quality, he has found the per centage of morphia to vary from 31⁄2 to 10. It requires little instruction in medicine to appreciate these facts.