52 KANSAS UNIVERSITY SCIENCE BULLETIN. 



Upper, respiratory curve, with lever attached to gill arch, shows first 

 decrease in rate for about one minute, then rate normal, force slightly in- 

 creased. Lower, cardiac curve, with lever attached to apex. Cardiac 

 activity unaltered. 



Curve 35. Urea 2m. 



Upper, Hiirthle cardiac record shows little increase in force and rate. 

 Lower, respiratory rate and force unaltered. 



Curve 36. Urea 4m. 



Upper, Hiirthle cardiac curve; increased in force and pressure, rate 

 unchanged. Lower, respiratory curve; force slight rise, rate unchanged. 



The results obtained with standardized HCl solutions are 

 tabulated in table IX. The v^eaker solutions, ranging from 

 m/100 to m/64, increase for the first minute or two the force 

 of the cardiac and respiratory and blood-pressure changes, and 

 decrease or act indifferently on the rate of respiratory and car- 

 diac activity. A stronger solution, m/32, for the first minute 

 or two decreases the rate but usually increases the force of 

 both the respiratory and heart action, and the blood pressure 

 usually rises for the first minute ; m/8 is toxic, but the respira- 

 tory rhythm continues several minutes after the heart ceases, 

 or if it continues it is rapid and faint and the respiratory 

 movements are continued with less force and rate. It is sup- 

 posed that the stimulating action is due to the H ions. In all 

 concentrations between m/100 and m/16 there is an initial 

 increase in pressure and force, followed by a decrease in all 

 activities before a return to either normal or less. 



