572 



Miss D. J. Lloyd. 



solution must always be open to a variety of interpretations. The course of 

 events depends not only upon the initial state of the muscle but also upon 

 properties of the surfaces of muscle and muscle fibre considered as semi- 

 permeable membranes. Further, osmotic relations are complicated by change 

 in the muscle due to the chemical nature of the solution. Thus, to take salts 

 as examples, the sternocutaneous muscle in A molecular solution of sodium 

 chloride usually remains of constant weight for some time, and then loses 

 weight ; in a similar solution of potassium chloride there is an immediate 

 and prolonged rise in weight followed by a fall ; in an isosmotic solution of 

 calcium chloride there is a very small and fleeting initial rise in weight 

 followed by a long and steady fall which may reduce the muscle to 60 per 

 cent, of its original weight. 



It is possible, however, to examine the osmotic balance of a muscle by 

 exposing it to water vapour of varying pressure. The gas space round the 

 muscle then acts as a theoretically perfect semi-permeable membrane so far 

 as non-volatile solutes are concerned. The method adopted was to suspend 

 the muscle in a flask over a solution of known concentration, the gas in the 

 flask first having been shaken thoroughly with the solution and then left at 

 the desired temperature for some hours in order to attain equilibrium. The 

 muscle was removed for each weighing, and results therefore are affected by 

 an error due to loss of water during weighing, and loss of vapour from the 

 flask during removal and replacement. Control experiments with fine plates 

 of agar saturated with water gave a maximal loss of 3 per cent, in four hours. 



In fig. 4 are shown curves of the weight changes of muscles suspended in 

 oxygen above the plane surface of (b) distilled water, (c) - 06 molecular 



120- 



60 



Fig. 4. 



