xiii RESPIRATORY RHYTHM 495 



of the respiratory phenomenon, with the object of verifying whether 

 the two effects (which present such a marked analogy) had a 

 common origin. Since the cardiac effect is instantly and con- 

 spicuously obtained upon the isolated heart perfused with serum, 

 when the most automatic part of the frog's heart is cut off by a 

 ligature, we inquired whether the respiratory effect would be 

 produced, on transversely dividing the spinal bulb in the rabbit, 

 above the origin of the vagus nerves, so as to separate its highest 

 segment from the respiratory centres. These investigations 

 (carried out like the former in Ludwig's laboratory) were long 

 and laborious, because not always successful. Sometimes we 

 obtained respiratory standstill, immediately or soon after the 

 section. At other times there was no radical modification of 

 respiratory rhythm, which (although it became irregular and pro- 

 gressively slow and shallow till death occurred) never presented 

 the peculiar grouping characteristic of Cheyne-Stokes breathing. 



FIG. 233. Periodic respiration in rabbit, after transverse section of bulb at level of visible apex 

 of alae cinereae. (M. Marckwald.) Tracing taken with phrenograph. The ascending curves 

 correspond with the contractions of the diaphragm. 



But in other more fortunate cases it did appear in the form 

 of groups, which exhibited no increment but merely a rapid 

 decrement followed by the pause. The number of respirations 

 in the successive groups increased or diminished somewhat 

 irregularly ; at the same time the pauses became now longer, now 

 shorter than the groups. In the most successful experiment, 

 however, we were able to watch the tendency of the groups to 

 become gradually smaller, and of the pauses to shorten, till the 

 crisis of the phenomenon set in, when the groups resolved them- 

 selves into a series of staccato respirations separated by long 

 pauses, and progressively decreasing till death ensues. The vary- 

 ing position of the section on the bulb, and the different degrees 

 of the consequent haemorrhage, appear to us sufficient to account 

 for the difference in results. 



Marckwald (1888) obtained precisely similar results in 

 Kronecker's laboratory on separating the medulla oblongata from 

 the rest of the brain at a level above the respiratory centres of 



