"On the suggestion of Dr. Alzheimer I examined the following four cases." Dedicated to Gaetano Perusini.

Gaetano Perusini merits a great deal more credit for his work on the elaboration of the concepts regarding what is now called Alzheimer's disease (AD). Perusini's work in Alzheimer's laboratory and his subsequent studies have been, if not neglected, largely unmentioned. This article is an attempt to report a fascinating piece of medical history in order to redress the balance. Surely, Perusini's work deserves to be reexamined. The same applies to Fischer's investigation. Some of the puzzles discussed by Perusini are still unresolved.