Semifine heart section stained with toluidine blue and observed with the objective of 40x. We can perceive cardiac striated muscle fibers, surrounded by conjunctive tissue containing abundant blood vessels. The fibers, elongated and with ramifications in some cases, show a central nucleus and the characteristic intercalated discs, corresponding to unions between two consecutive fibers. Details of these structures are offered at higher magnification in other microphotography (zone framed in red)