IX 



CARDIAC MUSCLE AND NERVES 



301 



sheep's serum, by which a certain pressure was exerted on the in- 

 terior of the frog's heart, it began to beat again vigorously, regardless 

 of the point at which the ligature was applied. In order to study 

 the course of the heart's action under these conditions we connected 



FIG. 129. Paroxysm in form of ascending staircase, shown by frog's heart, filled with sheep's 

 senim, and tied at auriculo-ventricular groove, immediately after attachment to tonographic 

 apparatus. (Luciani.) ! 



the cannula with the excised frog's heart to a small recording 

 mercury manometer (Fig. 121), and then obtained the curves of 

 three distinct and quite characteristic phenomena, representing 



FIG. 130. Tetaniform paroxysm presented by frog's heart already attached to tonographic 

 apparatus, as the effect of a second ligature 2 mm. below the auriculo-ventricular groove. 

 (Luciani.) 



three different phases of cardiac activity, which precede the 

 exhaustion of the heart. 



The first phenomenon may be termed the " paroxysm " 



FIG. 131. Tetaniform paroxysm commencing at a, after ligature of auricles, converted at b into 

 an ascending staircase, by the momentary opening of the valve of the tonographic apparatus. 

 (Luciani.) 



(accesso), and consists in a sudden increase of cardiac muscular 

 tonus in conjunction with great frequency of beat. With 

 the progressive diminution of tone the beats become less 

 frequent, but are at the same time more ample in diastole, 

 since the presystolic filling of the ventricle steadily increases. 



