 It is impossible to present even a hint of the richness of the empirical content of the Historia Animalium here. Before going on to a discussion of the works that report the results of Aristotle’s causal investigations of animal parts and animal generation, however, two examples of reports from HA are provided for comparison with corresponding discussions in PA and GA. The first example discusses the organs of respiration in blooded animals; these are the first internal organs discussed after Aristotle has concluded his review of their external parts. Here is how he introduces that discussion.