The Practice of Medicine by Robley Dunglison (1844)
= The Practice of Medicine by Robley Dunglison (1844)
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https://upload.wikimedia.org/wikipedia/commons/c/c6/The_practice_of_medicine-_a_treatise_on_special_pathology_and_therapeutics_%28Volume_2%29_%28IA_63350860RX2.nlm.nih.gov%29.pdf
Second edition, volume 2, section Pityriasis. Four descriptive varieties and the objection that one usage of nigra lacks scaling. This is a pre-1865 text, not a modern taxonomy.