e was
firmly convinced that the skeleton in all the higher animals was built
upon one common plan and that accordingly bones such as the
intermaxillaries, found well developed in some animals, must also be
found in man. The idea was not drawn from the facts, but the facts
were interpreted and even sought for in the light of the idea. "I
eagerly worked upon a general osteological scheme, and had accordingly
to assume that all the separate parts of the structure, in detail as
in the whole, must be discoverable in all animals, because on this
supposition is built the already long begun science of comparative
anatomy."[72]

The principle comes to clear expression in his _Erster Entwurf einer
allgemeinen Einleitung in die vergleichende Anatomie_ (1795).[73] He
writes:--"On this account an attempt is here made to arrive at an
anatomical type, a general picture in which the forms of all animals
are contained in potentia, and by means of which we can describe each
animal in an invariable order."[74] His aim is to discover a general
scheme of the constant in organic parts, a scheme into which all
animals will fit equally well, and no animal better than the rest.
When we remember that the type to which anatomists before him had,
consciously or unconsciously, referred all other structure was man
himself, we see that in seeking after an abstract generalised type
Goethe was reaching out to a new conception. The fact that only the
structure of man and the higher animals was at all well-known in his
time led Goethe to think that his general Typus would hold for the
lower animals as well, though it was to be arrived at primarily from a
study of the higher animals. All he could assert of the entire animal
kingdom was that all animals agreed in having a head, a middle part,
and an end part, with their characteristic organs, and that
accordingly they might, in this respect at least, be reduced to one
common Typus. Goethe's knowledge of the lower animals was not
extensive.

Though Goethe did not work out a criterion of the homology of parts
with any great clearness, he had an inkling of the principle later
developed by E. Geoffroy St Hilaire, and called by him the "Principle
of Connections." According to this principle, the homology of a part
is determined by its position relative to other parts. Goethe
expresses it thus:--"On the other hand the most constant factor is the
position in which the bone is invariably found, and the function