536 Physico-Chemical Basis of Muscle Contraction [June 



THE AUTHOR'S CRITICISM OF THE ZUNTZ THEORY 



The theory contains many objectionable features. Some of 

 them are considered in the following brief review. 



In bis conception of the structure of human or frog muscle, 

 Zuntz assumes that the fibril consists of a string of muscle rods. 

 These rods exist in the living fibrils of certain insect muscles. The 

 writer has not yet found any statement to the effect that they have 

 been seen in frog or human muscle fibrils. Their existence in such 

 fibrils is somewhat of an assumption. 



His calculations contain the assumption that all of the oxygen 

 consumed by a working muscle is used for the maintenance of com- 

 bustion inside the rods, leaving no oxygen for the sarkoplasm, which 

 constitutes the larger part of the muscle. Furthermore, it is not 

 certain that when a molecule of fatty acid, for example, is burned in 

 a working muscle, the entire combustion process takes place within 

 the rod. It is possible that only a part of the entire heat of com- 

 bustion is liberated in the rods, and there transformed into external 

 work. 



Practically all of the resultant carbon dioxid is present in the 

 (sarkoplasm) lymph in a more or less strong combination with some 

 lymph constituent. Only a very small portion of the total amount 

 of carbon dioxid is present as gas in Solution. Gases such as carbon 

 dioxid and oxygen, when dissolved in water, do not behave entirely 

 like true solutes. Until the osmotic pressure of a gas in Solution has 

 been measured, the statement that carbon dioxid exerts an osmotic 

 pressure when dissolved in water sliould be regarded as one involv- 

 ing assumptions. This, of course, is not true of such gases as hydro- 

 chloric acid, ammonia, and a few others. 



In view of the fact that carbon dioxid, at about 2000° C. is dis- 

 sociated into carbon monoxid and oxygen, it is doubtful whether 

 the carbon dioxid molecules at the moment of their formation with- 

 in the muscle rod, have a temperature of 6000° C, as calculated by 

 Zuntz. If they did, there would be carbon dioxid dissolved, not in 

 water, but in steam (?) and under such conditions perhaps osmotic 

 phenomena would not come into play at all. 



It was not shown that the walls of the muscle rods are imper- 

 meable to carbon dioxid during the contraction phase. This is 



