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 thought which he probably owed to the German transcendentalists (see Chap. VII.), that the permanent structure of the lower animals could be compared with phases in the development of the higher, and particularly of man, or, as he put it, that comparative anatomy was often only a fixed and permanent anthropogeny, and anthropogeny a fugitive and transitory comparative anatomy (xi., p. 106).