The corpus callosum is a neopallial commissure. In inferior vertebrates, the pallial commissures are essentially represented by the anterior commissure. The corpus callosum appears in mammals only. Eutherians alone have a corpus callosum, the other mammals have an anterior commissure and hipocampal commissure. In humans, the different portions of the corps callosum are described on a median sagittal slice: rostrum, genu, body, isthmus, splenium. Klingler method allows to dissect fibers of each of these portions and their relationship with the corona radiata and optic radiations. These latter are separated from the ventricular ependyme by callosal radiations. Finally, each part of the corpus callosum participates in lateral ventricle wall formation.