[124] _Isis_, p. 539, 1820 (2).

[125] _Mammiferes_, i., _Lecon_ 4, p. 6.

[126] _Mammiferes_, Discours prel., p. 7.

[127] _Isis_, p. 460, 1820 (2).

[128] _Mem. Mus. d'Hist. nat._, ix., p. 102, 1822.

[129] _Mem. Acad. Sci._., xii., p. 76, 1833.

CHAPTER VI

THE FOLLOWERS OF ETIENNE GEOFFROY SAINT-HILAIRE

Geoffroy's theories were not generally accepted by his contemporaries,
but his methods had considerable influence, especially in France, where
many made essays in pure morphology.

His chief follower was Serres, who is mentioned indeed in the
_Philosophie anatomique_ as a fellow-worker. Serres was primarily a
medical anatomist; his interest lay in human anatomy and embryology,
normal and pathological.

His best early work was an _Anatomie comparee du cerveau_ (1824-26),
which met with a flattering reception from Cuvier.[130] He laid great
stress upon the development of the brain and spinal cord in the
different classes, and was quick to point out analogies not only between
adult but also between embryonic structures. He paid much attention to
cases of correlation, and noted a great many; he observed, for instance,
a constant relation between the development of the spinal cord and of
the corpora quadrigemina, and between the size of the corpora
quadrigemina and the volume of the optic nerves and eyes. In this the
influence of Cuvier is unmistakable.

Serres' early theoretical views are to be found in a series of papers in
the _Annales des Sciences naturelles_,[131] under the general title
_Recherches d'Anatomie transcendante, sur les Lois de l'Organogenie
appliquees a l'anatomie pathologique_, also published separately. We
follow these papers in our expose of Serres' doctrine, reserving for a
future chapter (Chap. XII.) the consideration of his matured views of
thirty years later.

In the first of them he points out how neither position nor function has
proved altogether sufficient to establish homologies. In the early days
anatomists were guided by form; when form failed them, they traced an
organ in its changes throughout the series of animals by considering its
function. This method was satisfactory enough as regards the organs of
the nutritive life. But in the organs of the life of relation, in the
nervous system, the functions of the parts were difficult to discover,
and their form very changeful. Hence a new principle was required, and
Serres found it in the though