Bundle of His is a network of : -

The conducting system of the heart (SA node, AV node, bundle of His and Purkinje fibres) is made of specialised (modified) cardiac muscle fibres, not nerve fibres. The heart is myogenic.
The bundle of His (AV bundle) starts from the AV node, passes through the interventricular septum, and divides into right and left bundle branches, which give rise to the Purkinje fibres spreading throughout the ventricular walls.
So it carries the impulse only to the ventricles; the atria receive the impulse directly from the SA node through the atrial muscle.
So the bundle of His is a network of muscle fibres found only in the ventricle wall.