In The Tomb of the Cybermen (1967), veins and brains were visible through the domed head of the Cyberman Controller and similarly, in Attack of the Cybermen (1985) and "The Age of Steel" (2006), the Cyber-Controller's brain is visible through the dome.
Veins and brains were visible through the domed head of the Cyberman Controller, In 1967 Tomb of the Cybermen and the 1985 Attack of the Cybermen; The Age of Steel" (2006), the Cyber-Controller's brain is visible through the dome.