STANNIUS' LIGATURE. 249 



Stannius' ligature. 1 No. 1. Arrange the pithed frog to 24 

 record by the suspension method, and pass a ligature under 

 the aortee, bring it round to the dorsal side of the heart, 

 and tie a loop ; apply this to the line of junction of auricles 

 and sinus, and ascertain that it is placed in contact with 

 the crescent, then draw it tight. The ventricle will stop 

 beating. This arrest always lasts for a considerable time, 

 and may be permanent. Failure is usually due to the ligature 

 not having been placed upon the crescent. 



Affix the light electrodes as for crescent stimulation only in 

 this case, against the ventricle itself, and arrange to stimulate 

 with single shocks. With a sufficient stimulus, the heart will 

 respond with a single contraction at each stimulus. 



Latent period. Place the drum contact in P circuit, 

 drum at a moderately fast speed. Inscribe a 1/10 second 

 time tracing on the paper. Bring the recording point into 

 contact with the paper for one revolution of the drum only 

 at a time. Mark the point at which the stimulus was thrown 

 in. Measure the duration of the period, and compare it with 

 that already obtained with striped muscle. 



Cardiac tetanus. After concluding the last experiment, 

 attempt to induce tetanus by stimulating the ventricle with 

 interrupter shocks. Cut out the drum contact and connect 

 the interrupter in the P circuit. 



It will be found that the most rapid succession of stimuli 

 will only yield an irregularly continued contraction, but so 

 far incomplete that individual twiches are still represented 

 upon the curve. 



1 Stannius' ligature. No. 2 is applied in a similar manner to the line of junction 

 of the auricles with the ventricle. It is followed by a revival of the ventricular beats 

 the auricles, however, remain at rest. 



