812 CONTRACTION-WAVE IN MTJSCLE 



Thre curves, those of the tuning-fork and of the contraction-waves 

 at two points of the muscle were thus described above one another. 

 Experiments with the rhythmically beating heart of Limulus re- 

 quired opening the shutters by hand just before a contraction of 

 the organ. 



Determinations were made to ascertain the time which should 

 elapse after a change of solution in order to enable the tissue to reach 

 a uniform condition and permit duplicate records to be secured. 

 This period, with frequent changes and stirring of the solutions in 

 the tumblers, was rarely less than 20 minutes in the smallest 

 frog muscle. During this time the records indicated gradual changes 

 in the speed of the contraction-wave. After a lapse of this initial 

 period records were taken at intervals duringan hour or more. These 

 related to the behavior of the tissue (a) in the normal medium, 

 Ringer's solution or sea water, {h) in a medium made by diluting the 

 normal medium with isotonic sugar solution, and (c) again in the nor 

 mal medium. The change in the behavior of the tissue on passing 

 from the normal medium of high conductivity to a medium of lower 

 conductivity could thus be compared with the change following the 

 reverse transfer. The rate of recovery of propagation-velocity on 

 returning from the medium of low conductivity to the normal medium 

 could also be determined. 



RESULTS. 



Limulus. — The experiments upon the heart of the king-crab were 

 designed to show {a) changes of irritability in pure isotonic sugar 

 solutions, {b) the behavior in mixtures of sea water with isotonic 

 sugar solution in various proportions, and (c) the behavior in sea 

 water under the same experimental conditions over a period equiva- 

 lent to that covered by the tests. The determinations of the pro- 

 pagation-velocity have been made over different distances and with 

 respect to different portions of the hearts. The most consistent 

 records are from the anterior third; while those from the posterior 

 and anterior region, i.e., covering the length of the whole organ, 

 are of doubtful value. In all cases the temperature of the solutions 

 employed has been adjusted to that of the sea water on the day of 

 the experiment. 



