376 SIR THOMAS R. FRASER AND MR ALISTER T. MACKENZIE ON 



twitches which shorten the muscle once more. Gradually, the shortening of the 

 muscle passes off, and usually it had entirely disappeared when spontaneous fibrillary 

 twitches had ceased (Plate IT. figs. 5 to 7). The jerking of the lever has been referred 

 to above. After the initial shortening of the muscle occurs, the fibrillary twitches to 

 which this is due are very noticeable. These soon become very coarse and incessant, 

 and thereafter become less frequent and finer, until they disappear entirely. Even 

 after spontaneous fibrillary twitches have disappeared, coarse fibrillary twitches may 

 be caused for a time by stimulation of the muscle, and, at any time during which 

 fibrillary twitches are present, they become more coarse and more frequent after 

 contraction and relaxation of the muscle. Such twitches are seen in Plate III. fig. 5. 

 After the cessation of spontaneous fibrillary twitches, changes in the muscle curve 

 appear. Usually the first change is that the poisoned muscle requires stronger stimuli 

 to cause contraction. When it contracts, its curve is not so high as that of the 

 non-poisoned muscle ; the rise of the lever is more gradual, the summit of the curve is 

 more rounded, and the fall of the lever much slower than in the case of the control, 

 as in Plate II. fig. 7 and Plate III. figs. 7 and 9. Finally, the poisoned muscle fails 

 to respond to strong electrical stimuli long before the non-poisoned muscle does so. 



E. Effects on the Circulation. 



(a) Heart. 



From the earliest experiments, both in cold-blooded and in warm-blooded animals, 

 it was obvious that S. sarmentosus has an action upon the skeletal and cardiac 

 muscles in comparison with which its other effects are of secondary importance. 

 The heart- muscle seemed to be particularly sensitive. Observation of the cardiac 

 impacts revealed that these were at first increased in rate, in force and in extent ; later, 

 they became irregular in rate and in force ; and just before death they were feeble, 

 irregular and difficult to determine. When the heart was exposed immediately after 

 death, it was usually found that the heart's ventricle was motionless, pale and firmly 

 contracted ; it did not respond to mechanical or electrical stimuli, direct or indirect, 

 and soon became acid in reaction. In the case of warm-blooded animals the left 

 ventricle of the heart showed these characteristics more distinctly than did the right. 

 Experiments to determine more exactly the extent and the nature of this action upon 

 the heart will now be considered. 



The following experiment shows the effects upon the frog's heart of a dose of 

 the extract, subcutaneously injected, which caused profound general effects, but from 

 which the frog would probably have recovered : — 



Experiment LII. — Sixty-eight hours 20 minutes after receiving into the dorsal 

 lymph-sac a dose of extract equal to 0*0031 gram per kilogram, the frog (Rana 

 esculenta) lay on the abdomen and thorax with the limbs loosely flexed ; the throat 



