PHYSIOLOGY OF SMOOTH AND STRIATED MUSCLE 539 



what above that of the surrounding half strength Ringer solu- 

 tion, and during this period equal quantities of water would enter 

 the muscle fibers in equal periods of time. 



A generally similar explanation may be given for the curve 

 which represents the loss of weight by the muscle in double 

 strength Ringer solution. In this case the increasing concentra- 

 tion of the salts within the fibers due to the loss of inorganic water 

 would cause the colloids to give up some of their organic water, 

 and the curve of loss of weight would take the form of a straight 

 hne for the same reasons as in the case of the hypotonic solution. 



It is interesting to observe that the curves representing the loss 

 of weight by striated muscle in hypertonic solutions are more 

 regular than those representing the gain of weight in hypotonic 

 solutions (compare fig. 4 with figs. 5 and 6). The irritability of 

 striated muscle is increased by immersion in hypotonic solutions 

 and decreased by immersion in hypertonic solutions. After a 

 few minutes' immersion in half strength Ringer the tissue often 

 twitches as a result of the mechanical stimulation which accom- 

 panies the process of drying and weighing. It may well be that 

 the irregular chemical activity which is expressed in this twitching 

 is the cause of the irregularity of the later part of the curve of 

 water intake. 



Experiments 12, 17, 32 and 56 furnish evidence for the view that 

 under certain conditions the muscle membranes may become 

 somewhat permeable to the muscle salts, though the irritability 

 of the tissue is not appreciably affected. It is shown in these 

 experiments that striated muscle immersed in half strength Ringer 

 first gains and then loses weight, though it remains quite irritable 

 through the whole course of the experiment. The loss of weight 

 may most readily be accounted for by supposing that some of the 

 potassium phosphate, which gives to the muscle fluid its normal 

 osmotic pressure, diffuses out of the fibers in the course of the 

 experiment. 



The situation with regard to striated muscle may be summed 

 up by saying that osmosis plays an important part in the changes 

 of weight which the tissue undergoes when immersed in various 

 solutions, but that important parts are played by other factors 

 also. 



