PHYSIOLOGY OF SMOOTH AND STRIATED MUSCLE 509 



and the resulting contraction lasted only a fraction of a second, it 

 may be supposed that the chemical change produced had a negli- 

 gible effect on the course of the tissue's changes in weight. A good 

 deal more manipulation was necessary to satisfactorily test the 

 irritability of the preparations of smooth muscle. Where this 

 did not have to be done until the end of the experiment, strips 

 were cut off from the actual piece of muscle which had been 

 weighed, and tested as described above: when it was desirable to 

 test the irritability of the smooth muscle in the middle of an experi- 

 ment, the piece of muscle used was cut into a strip and a larger 

 sheet and the two portions were immersed in the solution; the 

 strip was used for the testing of irritability and the larger sheet for 

 weighing. 



It w411 be noticed that it is reported at the end of some of the 

 experiments that pieces of smooth muscle showed a tendency to 

 lengthen on stimulation. This seemed to be the case after the 

 tissue had remained fof some time in various solutions, but partic- 

 ularly as the result of immersion in double strength Ringer solu- 

 tion. Subsequent experiments, in which the changes of length 

 undergone by the tissue as the result of stimulation after a stay 

 in double strength Ringer, were recorded on a kymograph instead 

 of being studied as described above, showed that the stimulation 

 usually produced a very small shortening followed by a compara- 

 tively large lengthening. In only a few cases did the preliminary 

 shortening fail altogether to appear. 



The results of some of the experiments are given in curves, 

 which appear throughout the article. In these the points of 

 weighing are prominently indicated by crosses. 



Some of the experiments give the results of immersing connec- 

 tive tissue in various solutions. The connective tissue was 

 obtained from the tendo AchiUis of large frogs, and the technique 

 w^as the same as in the experiments on muscle. 



A few of the experiments give the results of attempts to deter- 

 mine directly by chemical analysis to what extent sodium and 

 potassium diffuse out of smooth muscle into a surrounding iso- 

 tonic sugar solution, and to what extent the sugar diffuses into 

 the muscle. These experiments require no particular comment 

 in this place. 



