Islet Hyalinization as illustrated by E.L. Opie, 1900.
The detailed histology of pancreatic islet hyaline degeneration were first described by E.L. Opie. It was identified as amyloid, an extracellular proteinaceous material and can occur in diabetes mellitus and would set the precedent for further research into its pathogenesis.
What I find remarkable about the above diagram is that they were illustrated by hand by Opie more than a century ago. The detail is phenomenal. In class, we did not even realize they were illustrations until after the professor told us.