A Note on the Structure of the Elastica Interna

A comparison of a number of texts, descriptive of the structure of the elastic intima-the fenestrated membrane of Henleof arteries, reveals the fact that the views concerning the structure of this layer are byno means unanimous. Schafer‘ speaks of the elastic intima as follows: “The elastic tissue is represented by one distinct lamina, which is separated from the endothelium by the subendothelial layer. It is, on its outside, in direct contact with the non-striped muscle of the middle layer.’’ The ‘internal elastic lamina’ is spoken of as membranous in character, the membrane is not, however, a continuous one, but is perforated by apertures. In figure 517, of Schafer’s text, is shown a portion of the fenestrated membrane from the femoral artery as figured by Henle. Mall2 in his study of connective tissue fibrils states that “elastic fibers are composed of two distinct substances-the interior, which stains intensely with magenta, and the membrane, which does not.” A study of the membrane of Henle, isolated by boiling in acetic acid or KOH and then stained with magenta or picrocarmine leads him to conclude that “The Henle’s fenestrated membrane is therefore composed of three layers-an upper and a lower transparent membrane in which there are no openings, and which is identical with the membrane of elastic fibers; and a middle layer which stains with magenta, and is identical with the interior of elastic