 As many as (hosa) are four legged and live-bearing all (panta) have an esophagus and windpipe, arranged just as in human beings; it is also arranged similarly in as many of the four legged animals as lay eggs, and in the birds; but they differ in the forms (tois eidesi) of these parts. Generally, all and only (panta hosa) those receiving air by inhaling and exhaling in every case (panta) have a lung, windpipe and esophagus; and the position of the esophagus and windpipe is alike in all, but the organs are not, while the lung is neither alike in all nor is it positioned in a like manner. And again as many as (hosa) have blood all (panta) have a heart… . But not all [blooded animals] have a lung, for instance fish do not, nor any other animal there might be that has gills. (505b23–506a12, excerpts)