The applicability of Hermann's theory of alteration

Abstract

1. Herrmann's theory of alteration, which is accepted to-day by many physiologists, assumes that the junction of dead and of living tissue is the seat of an electromotive force which acts in such a direction that the dead tissue is negative while the living tissue is positive. This theory was advanced by Herrmann against DuBois Reymond who tried to explain the currents produced by muscles and nerves by means of complicated structural assumptions. Herrmann's theory has the advantage of expressing in an extremely simple form a large number of physiological observations. It has met general recognition partly also because all the opposing theories were of a very unsatisfactory character. The arguments however which Herrmann advances to support his views are not so conclusive as to fully justify his views. Especially his observation that a definite time elapses between the cutting of the muscle and the appearance of the current of injury must not necessarily be due to a chemical alteration resulting from the injury. This time is so exceedingly short (5/1000 of a second) that a mechanical explanation rather suggests itself than a biochemical.

2. The conception that a difference of chemical processes in the dead and in the living tissue produces currents is also contradictory to physical laws. This was already pointed out by DuBois Reymond and his arguments seem still valid to-day. According to well-established physical principles an E.M.F. may be produced as a result of a chemical alteration which is brought by a current passing through the system, not however through a local chemical reaction which liberates ions.

3. Moreover certain experimental facts are in direct contradiction to Herrmann's theory; if a muscle is brought in contact at one end with distilled water and at the other end with a physiological NaCl solution it is found that the part in contact with the water is positive.