[1] See Aristotle’s Zooelogy, Book I., Chapter xiv.

Strange that in Aristotle’s day, two thousand years ago, such books should have been in general use, and that in our time we are still in want of elementary text-books of Natural History, having special reference to the animals of our own country, and adapted to the use of schools.  One fact in Aristotle’s “History of Animals” is very striking, and makes it difficult for us to understand much of its contents.  It never occurs to him that a time may come when the Greek language—­the language of all culture and science in his time—­would not be the language of all cultivated men.  He took, therefore, little pains to characterize the animals he alludes to, otherwise than by their current names; and of his descriptions of their habits and peculiarities, much is lost upon us from their local character and expression.  There is also a total absence of systematic form, of any classification or framework to express the divisions of the animal kingdom into larger or lesser groups.  His only divisions are genera and species:  classes, orders, and families, as we understand them now, are quite foreign to the Greek conception of the animal kingdom.  Fishes and birds, for instance, they considered as genera, and their different representatives as species.  They grouped together quadrupeds also in contradistinction to animals with legs and wings, and they distinguished those that bring forth living young from those that lay eggs.  But though a system of Nature was not familiar even to their great philosopher, and Aristotle had not arrived at the idea of a classification on general principles, he yet stimulated a search into the closer affinities among animals by the differences he pointed out.  He divided the animal kingdom into two groups, which he called Enaima and Anaima, or animals with blood and animals without blood.  We must remember, however, that by the word blood he designated only the red fluid circulating in the higher animals; whereas a fluid akin to blood exists in all animals, variously colored in some, but colorless in a large number of others.

After Aristotle, a long period elapsed without any addition to the information he left us.  Rome and the Middle Ages gave us nothing, and even Pliny added hardly a fact to those that Aristotle recorded.  And though the great naturalists of the sixteenth century gave a new impulse to this study, their investigations were chiefly directed towards a minute acquaintance with the animals they had an opportunity of observing, mingled with commentaries upon the ancients.  Systematic Zooelogy was but little advanced by their efforts.