Hermann's Theory of Alteration. 



173 



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 ex- 

 planation 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 contra- 

 diction to Herrmann's theory; if a muscle is brought in contact 

 at one end with distilled water and at the other end with a physio- 

 logical NaCl solution it is found that the part in contact with the 

 water is positive. This means that the injured part of the tissue 

 is positive in this case since the distilled water has a destructive 

 influence in direct contradiction to the alteration theory. Bieder- 

 mann 1 who first observed this phenomenon has tried to bring it 

 in harmony with the alteration theory. He argues that the death 

 of the tissue produced by means of distilled water is of a peculiar 

 nature because the conduction of irritation still persists under 

 certain circumstances. This argument however certainly also 

 contains hypothetical factors. 



4. Mac Donald' 2 has described interesting experiments which 

 show that the magnitude of the current of injury has no relation 

 to the state of life or death of the tissue. The current of injury of 

 a sciatic nerve of the cat is measured immediately after excision 

 and some time later; it is then generally found that the magnitude 

 of the current decreases, which might be explained as being due to 

 the death of the nerve. If however the nerve is immersed for a 

 short time in a dilute salt solution the magnitude of the current 

 of injury increases up to or above the original value. It hardly 

 need be said that this treatment does not restore to the nerve any 



'Sitz. d. Wiener A kadem., 81, Abt.3, 74 (1880). 

 1 Proc. Roy. Soc, 67, 310 (1900). 



