The Osmotic Balance of Skeletal Muscle. 



569 



weight with time is, I think, sufficient proof that the error was reduced to 

 about 1 per cent, of the total weight. 



According to the definition of an isotonic solution given above, such a 

 solution does not, strictly speaking, exist. A muscle may remain steady 

 within the limit of error of weighing for periods up to half-an-hour, but sooner 

 or later measurable variations of weight appear. In other words the muscle 

 removed from the body is a changing system. It is a question whether the 

 apparently steady periods are not really periods of very slow change. It is 

 noteworthy that different workers have fixed upon solutions of sodium chloride 

 over such a wide range as from 0*6 to 0*8 per cent, as being isotonic with 

 frog's muscle ; and the only curve given by Fletcher of a muscle in an isotonic 

 solution shows a steady rise in weight. 



A muscle simply removed from the body is called by Fletcher a resting 

 muscle. The use of the term is inadvisable. Such a muscle has suffered a 

 certain amount of mechanical disturbance, and in the process of pithing the 

 frog it has been thrown into tetanus lasting a minute or more, at a time 

 when the circulation of blood is defective. Such a muscle is best indicated 

 by the term untreated muscle. 



The weight changes characteristic of an untreated muscle in solutions of 

 the sugars biose, dextrose, sucrose, and rafhnose between the concentrations 

 zero to - 27 molecular are shown in fig. 1, which shews a curve for 



160 



Fig. 1. — Abscissas = hours from beginning of experiment ; Ordinates = weight of muscle 

 expressed in percentage of initial weight. 



