Lecture XIV

Many things are discussed in our physiological text books: we should fix our attention elsewhere, on subjects whose existence is admitted but whose significance is constantly under-rated. Here is one instance. You are able to observe—quite macroscopically and as it were in a commonplace way—that the epidermis covers the human body, and has various inward folds or pockets; and its continuing membrane lines the parts situated to the interior. This is very important—the reversal of functions, as, e.g., we find it in passing from the cheeks and the external parts of the face, over the edge of the lips to the interior. There indeed one finds, in the external formation of man, the vestige of the process which where all development really proceeds by means of folding inwards and invaginations. In following up the differences in the reaction of the upper epidermis and the internal mucous membrane to preparations of formic acid, and fully realising the delicate differences in these results, one would reach tremendous results. For all the facts I here set before you are really nothing but specialisations of the elementary structural principle indicated. The study of these facts will bring before you the whole polar opposition of that external lining (also etherically) of the human organism and that which goes inside and becomes central in the same organism.