The early development of the human diencephalon

The deyelopmental history of the mammalian diencephalon should offer the best basis from which the complex adult mammalian thalamus might be homologized or contrasted with the thalamus of lower vertebrates, yet 'few detailed studies of the embryology of this part of the forebrain have been made. The classical work of His ( '04)' on the early development of the human brain, describes the appearance of six fiber tracts within the diencephalon, but does not include the nuclear development of this region. Streeter ('12) and Hochstetter ('19) have given adequate descriptions of the morphological development of the human diencephalon, but have not investigated the differentiation of the nuclei and tracts. Grunthal ('30) and Kuhlenbeck ('30) studied the diencephalon in a few human embryos, but did not follow the ontogenetic history of the regions which they identified. Windle ('32 and '33) has made careful studies of the fiber connections of the diencephalon in young cat embryos by means of pyridine silver preparations, in connection with his study of the development of fetal behavior. Bianchi ('09), F'ortuyn ('12), and Miura ('33) have made detailed studies of the development and differentiation of the diencephalon in the rabbit, and on the basis of their observations they have drawn some conclusions regarding the phylogenetic relations