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During the past half-century, there has been recurrent interest in the chemical nature of the stinging capsules of cœlenterates. Mainly two lines of investigation have been pursued. Toxic extracts of the tentacles or whole animal have been examined1, and histochemical studies have been made. Both these approaches have yielded interesting information for speculation, but as Hyman2 has pointed out, “On the whole it must be concluded that the nature of the nematocyst toxin is unknown, since the extracts mentioned above include tissues as well as nematocysts …”, and one cannot expect the histochemical approach to yield the definitive answers.

Normal mitral valve function is dependent upon several structures other than the valve leaflets alone. These structures are in anatomic continuity from the atrial muscle to the ventricular muscle and, in addition to the leaflets, include the valve ring, the chordae tendineae, conduction tissue, and the papillary muscles. For perfectly normal valve function, each of these structures must be (1) anatomically and functionally intact, (2) in appropriate spatial interrelationship, and (3) operative in correct temporal sequence with respect to related structures. Obviously, normal mitral valve function is dependent upon a rather complex and finely coordinated system. In the past, of all the structures in this system, the papillary muscles have received the least interest and study. Yet they are of paramount importance, and disturbances of their function are a common cause of mitral valve incompetence. Pathophysiology Causes of papillary muscle dysfunction may be outlined as follows: Circulatory insufficiency (ischemia) Angina