Image extracted from “Pathogenic micro-organisms. A text-book of microbiology for physicians and students of medicine. (Based upon Williams’ Bacteriology)” by Ward J. MacNeal and Herbert U. Williams (1920) illustrating “Trypanosoma rotatorium, the various forms which occur in artificial culture” (original publisher: Philadelphia, P. Blakiston’s Son & Co.; contributing library: Cornell University Library; digitalizing sponsor: MSN; retrieved via Flickr); image modified by MIC. The cover is published under the Creative Commons Attribution (CC BY) license.