logical works are: "On the Motion of Animals;" "On
Respiration;" "Parva Naturalia;"--a series of essays which are planned
to form an entire work on sense and the sensible.

"The History of Animals" is the largest and most important of
Aristotle's works on biology. It contains a vast amount of information,
not very methodically arranged, and spoiled by the occurrence here and
there of very gross errors. It consists of nine books.

The first book opens with a division of the body into similar and
dissimilar parts. Besides thus differing in their parts, animals also
differ in their mode of life, their actions and dispositions. Thus some
are aquatic, others terrestrial; of the former, some breathe water,
others air, and some neither. Of aquatic animals, some inhabit the sea,
and others rivers, lakes, or marshes. Again, some animals are
locomotive, and others are stationary. Some follow a leader, others act
independently. Various differences are in this way pointed out, and
there is no lack of illustration and detail, but a suspicion is excited
that the generalizations are sometimes based upon insufficient facts.
The book closes with a description of the different parts of the human
body, both internal and external. In speaking of the ear, Aristotle
seems to have been aware of what we now call the Eustachian tube, for he
says, "There is no passage from the ear into the brain, but there is to
the roof of the mouth."[4]

In the second book he passes on to describe the organs of animals. The
animals are dealt with in groups--viviparous and oviparous quadrupeds,
fish, serpents, birds, etc. The ape, elephant, chameleon, and some
others are especially noticed.

The third book continues the description of the internal organs.
References which are made to a diagram by letters, _a_, _b_, _c_, _d_,
show that the work was originally illustrated. At the close of this
book Aristotle has some remarks on milk, and mentions the occasional
appearance of milk in male animals. He speaks of a male goat at Lemnos
which yielded so much that cakes of cheese were made from it. Similar
instances of this phenomenon have been recorded by Humboldt, Burdach,
Geoffroy St. Hilaire, and others.

In the first four chapters of the fourth book the anatomy of the
invertebrata is dealt with, and the accounts given of certain mollusca
and crustacea are very careful and minute. The rest of the book is
devoted to a description of the organs of sense and voice