On Anatomy (Anat.) is the shortest treatise preserved in the Hippocratic Corpus (HC). It describes the internal configuration of the human trunk. The account is for the most part descriptive, function being largely disregarded and speculation completely eschewed. Though systematic it is unsophisticated: two orifices for ingestion are linked by miscellaneous organs, vessels, and viscera to two orifices for evacuation. There is a clear progression in two parallel sections: first, trachea to lung, lung described, location of heart, heart described, kidneys to bladder, bladder described, bladder to genitals, conclusion; and second, oesophagus to belly, location of diaphragm, location of spleen, location and description of belly (close to liver), belly to intestine/colon, colon to rectum and anus, conclusion. The text offers good basic topographical or regional anatomy (the organs studied as they lie in relationship with one another in the different regions of the body). That the work is concerned with human anatomy is certain from the precise description of lung and liver, with features peculiar to human organs; and is corroborated by frequent references to comparative anatomy, with which familiarity is apparently assumed. Such anatomical knowledge, based on extensive observation of animals (probably sacrificial victims as well as laboratory specimens), may have been corroborated by some human dissection, perhaps of the aborted foetus or exposed infant, in conjunction with opportunistic observation of war wounded and accident victims. While the syntax is bald, telegraphic, and asyndetic, the vocabulary is recondite, and poetic. There is erratic omission of the article and recurrent use of compendious comparisons. These features suggest that Anat. may be an abridgement of a fuller and more flowery account; this hypothesis is supported by several passages where erroneous or unclear information apparently results from excessive compression or imperfect comprehension of a source.