HYDE: EXPERIMENTS ON THE SKATE. 3d 



KCl solution produces a first effect of from twenty seconds to 

 one minute upon the heart and respiratory activities. More 

 often during this time the heart rate is slower, due to prolonged 

 diastole, and the force remains unchanged. The inspiratory 

 phase is, however, lessened while the expiratory is relatively 

 prolonged. 



Curves 6 and 7 represent records obtained with different 

 methods after injecting an m/S KCl solution. Although many 

 other records were made these were chosen because they rep- 

 resent the more general type. There were exceptions in every 

 case, but those variations were accounted for either because 

 of the morbid condition of the skate, because it had been in the 

 aquarium several days, or had been under observation for sev- 

 eral hours and was fatigued or more or less irritable. After 

 the solution was injected for from twenty to sixty seconds the 

 heart activity greatly decreased and diastole was much pro- 

 longed. Occasionally the action increased above the normal 

 rate for one to two minutes, and in ten to fifteen minutes was 

 normal. The force remained unchanged. The respiratory 

 rate as a rule decreased for fifteen to thirty seconds, with 

 prolonged inspiratory phase, then either suddenly increased 

 above normal or gradually returned to the normal rhythm. 

 The force was usually unchanged. The blood pressure either 

 fell or increased slightly, about 2 mm. mercury, for from one 

 to two minutes. 



Following the injection of m% KCl, pressure fell either very 

 suddenly to zero or in rapid leaps from 20 to 16 in one minute 

 and zero in two minutes, or often 19 to 22 in one minute then 

 zero within three minutes. The heart decreased in rate; e. g.. 

 from 30 to 18, with increased force in one and zero in two 

 minutes. Respiration slowed from 39 to 30 in five seconds to 

 18 and very shallow and often irregular and spasmodic in ten 

 minutes, or rapid, 46 to 60, in five seconds, and gradually to 

 zero in seven minutes, but in some cases continued active as 

 long as twenty minutes after the heart had ceased contracting. 



A resume of the effects of KCl solutions brings to light that 

 diastole and inspiratory phases are prolonged above normal in 

 the different strengths of solution. Blood pressure falls in all 

 but the most dilute solutions. The force of the heart and res- 

 piratory activity is practically unchanged in all but the toxic 

 strength, m%, after which it decreases. The rate of the heart's 



