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Miss D. J. Lloyd. 



the medium, and partly on the configuration of the muscle colloids, is 

 confirmed by researches recorded in this paper which show that the excised 

 muscle is a labile system whose configuration depends on (at least) two 

 variables: (l)the hydrogen ion concentration, (2) the salt concentration. 



It should be noticed that in order to explain the swelling and shrinking 

 of muscle on an osmotic basis, there is no need to postulate a semi- 

 permeable membrane at its surface. Moore and Koaf and Webster (14) 

 have urged that the so-called " semi-permeability " of a membrane depends 

 more on the properties of the colloid behind the membrane than on the 

 membrane itself, and in the case of muscles it is easy to show that a muscle 

 which has been coagulated in distilled water (or any other neutral solution) 

 swells immediately on being put into acid or alkaline solution. 



So far the properties of excised muscle have been considered purely as 

 a non-living colloidal system. There seems little doubt, however, that the 

 same type of change occurs during life. Eanke(19), Loeb(ll), Fletcher (4), 

 and others have shown that the osmotic pressure of muscle rises after 

 fatigue, and the work of Fletcher and Hopkins (5) on the increased lactic 

 acid content of fatigued muscle leaves little doubt that this increased 

 osmotic pressure is due to the increased hydrogen ion concentration. 

 Barcroft and Toyojiro Kato, working on dogs (2), and Cogan, Back, and 

 Towers (1), working on the frog, have shown that fatigued muscles take up 

 water from the body fluids in situ, and this must surely again be due to the 

 acid produced. 



Ringer in 1883 stated that cardiac muscle will not contract in an. acid 

 medium, and that the heart of the frog, perfused with neutral saline until 

 the contractions cease, can be restored by making the solution alkaline. 

 Ringer, who also was aware that the contractions in heart muscle caused 

 the production of acid, considered that the alkalinity of the blood preserved 

 the tissues by preventing accumulation of acid (22). It is suggested below 

 that in the case of the skeletal muscles, whose activity is much more 

 irregular than the cardiac, it is also important to keep the acidity high 

 enough. 



Ringer showed for cardiac muscles that loss of contractility does not mean 

 simultaneous death of the tissue. The same is true for the excised skeletal 

 muscles. All the changes described in the foregoing paper are reversible in 

 their early stages. The sterno-cutaneous muscle of the frog, which is swelling 

 in isotonic potassium chloride, can be restored for 15 minutes after loss of 

 contractility, by being placed in isotonic sodium chloride. The same is true 

 for muscles which are losing weight in isotonic (0 - l molecular) calcium 

 chloride. These also can be restored to their normal function for about a 



