534 EDWARD B. MEIGS 



increase in the volume of the individual fibers brings about an 

 increase in their length and vice versa. 



The NaCl and KCl solutions would not affect all the fibers of 

 the preparation in the same way at the same time. In the NaCl 

 solution, for instance, the outer fibers of the preparation would al- 

 ready have passed through the stage of swelling and lengthening, 

 and would have begun to lose weight and shorten while the inner 

 fibers were still swelling. And in the KCl solution, the outer fibers 

 would begin to swell long before the inner ones had completed 

 the stage of losing weight and shortening. As the preparations 

 are allowed to lie in the solutions with their ends unattached, the 

 shortening of a very few fibers would show itself as a shortening 

 of the whole preparation, and this is no doubt the reason why the 

 shortening begins in NaCl before the loss of weight is marked; and 

 lasts far into the period of gain in weight in the KCl solution. 

 In Experiment 35, the muscle was not examined until after it 

 had been for more than three hours in the NaCl solution, and the 

 period of marked lengthening is, therefore, not recorded. 



It has already been said that smooth muscle varies in the 

 amount of fluid which it takes up from Ringer's solution. Other 

 things being equal, the tissue takes up more fluid at room tempera- 

 ture than at from 0° to 1°, and the muscle from the larger frogs of 

 a given species tends to take up more fluid than that from the 

 smaller frogs. In these cases also the changes in weight and 

 length go hand in hand — the muscle from the larger frogs of a 

 species lengthens more in Ringer's solution than that from the 

 smaller frogs, and smooth muscle lengthens much more in Ringer's 

 solution at room temperature than at from 0° to 1° (Experiments 

 18, 19, 20, 27, 31, 36 and 53). 



Experiments 33, 55 and 57 show that when the mechanical 

 stimulation which is inseparable from drying and weighing a 

 piece of smooth muscle happens to cause it to shorten, it causes 

 it also to lose weight. In the case of Experiment 52, the drying 

 and weighing did not cause any noticeable shortening and failed 

 also to cause the muscle to lose weight. 



The changes of length undergone by smooth muscle in Ringer 

 solution, in which small quantities of lactic acid have been sub- 



