From the National Archives:
Mid-19th-century doctors treated diseases and wounds with herbal cures. Using natural medicines was especially widespread in the Confederacy because the Union naval blockade prevented the importation of medicines. The Confederate Surgeon General created several laboratories that manufactured drugs from plants and herbs.
I couldn’t find much about W. B. Robertson, except that his surgical instruments are housed at the Louisiana State Museum, and the Virginia Marine Resources Commission lists him as having directed the agency from 1875 until 1877.