210 KANSAS UNIVERSITY SCIENCE BULLETIN. 



these stimuli and the contractions of the diaphragm resulting 

 from the stimuli emanating from higher centers in the brain 

 were recorded and compared. If the phrenic nerve or any of 

 its branches are stimulated with the weakest possible current, 

 it is responded to, throughout the period, by a contraction of 

 the diaphragm or an inspiration phase of the side stimulated. 

 The efficiency of the tripolar electrical block was compared 

 with others, especially those produced by cocaine and freezing 

 mixtures, and liquid air. 



It was found that the contractions of the diaphragm were 

 suppressed the instant and throughout the period that the 

 tripolar block was closed. The strength of the block current 

 was not more than (2.8)- volts, and this strength would sup- 

 press the cranial or naturally aroused impulses, as well as 

 those originated by the very weakest faradic current. Only 

 in one experiment did a block of (1.4)- volts inhibit the 

 cranial but not the artificially aroused impulses. 



But cocaine, a freezing mixture of sodium chloride and ice, 

 or liquid air, proved efficient in suppressing the impulses 

 originated by the higher centers in the phrenic as well as 

 those produced by electrical stimuli. 



The presence of afferent fibers in the phrenic was well 

 demonstrated by a simple experiment. When the motor im- 

 pulses on one side were blocked, and the phrenic stimulated 

 centrally to the block, a change in rate and amplitude of the 

 diaphragmatic movements of the opposite followed, as was 

 indicated by the contraction curves secured from the dia- 

 phragm slips on that side. The same result was obtained 

 when the phrenic of one side was cut and the central cut end 

 stimulated. Stimulating or irritating the peritoneum in dif- 

 ferent regions of the abdomen with intact phrenic is followed 

 by a change in rate and force of the respiratory movements. 

 This is, however, probably due to afferent stimuli from nerves 

 other than the phrenic to the respiratory center. 



