The 'Bundle of His' (or atrioventricular bundle) is a crucial part of the heart's electrical conduction system. It is composed of specialized cardiac muscle fibres, not nerve fibres. It originates from the AV node, which is located near the junction of the atria and ventricles, and then extends down into the interventricular septum, where it branches into the left and right bundle branches. These branches distribute the electrical impulse throughout the ventricles, leading to ventricular contraction. While it originates near the atrial-ventricular border, its structure and function are primarily associated with conducting impulses to and within the ventricles. Option C correctly identifies its composition as muscle fibres and its primary location within the ventricle (including the septum which is functionally part of the ventricular conduction pathway).