This diagram showing a medical cross-section of Godzilla was created in 1967 by Shogo Endo for a book called An Anatomical Guide to Monsters. Apart from Godzilla it contains a variety of anatomical drawings of many other kaijus, including Mothra, Gamera and Agurius.
I don't know the names of the rest of these guys, if you do, please feel free to kinja them.
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