The Osmotic Balance of Skeletal Muscle. 



571 



The region between 0*21 molecular and - 27 molecular for the sugars is one 

 in which the initial intake may or may not appear. The muscle either at 

 once loses weight after a short period of slight change, or shows a typical 

 initial intake followed by a typical loss. The variation over the region may 

 provisionally be attributed to a variation in the state of the muscle due to 

 mechanical disturbance. For instance, in dissecting the muscle out it is 

 subjected to a varying amount of tension, and this will tend to produce 

 passage of fluid from the interior of the fibre to the lymph space or vice versd, 

 and pithing the frog causes fairly prolonged twitching when the blood flow is 

 poor. If it were possible to secure muscles in a definite physiological state 

 this diffuse zone would probably narrow to a critical concentration, below 

 which the initial intake would occur and above which it would vanish. Some 

 part of the initial intake of water from hypotonic solution is unquestionably 

 due to the mechanical disturbance of the muscle. 



Effect of Oxygen. — Fletcher found that the osmotic changes induced in a 

 muscle by activity were removed by exposure to oxygen. The muscle was 

 put back into the " resting " state, which was characterised by a large 

 intake of water from hypotonic solutions. My results with the sterno- 

 cutaneous do not readily harmonise with those of Fletcher. The effect of 

 previous exposure to oxygen is to reduce, and finally to obliterate, the initial 

 intake of fluid even from distilled water. In fig. 3 are two curves, (a) from a 

 muscle put directly after removal from the body into distilled water, (b) from 

 a muscle placed in distilled water after three hours' exposure to moist oxygen. 



-o o — a 



o- b 



Fig. 3. 



It might be urged that the intake has already taken place from the water 

 vapour during exposure to oxygen. This is not so. Muscles in oxygen and 

 water vapour always tend to lose weight. If any intake does occur it must 

 be so transitory and slight as to have escaped detection. 



Exposure to Water Vapour. — The behaviour of a muscle immersed in a 



