THE RESPIRATORY CENTRE 

 Table II — continued 



91 



The following are considered the most noteworthy characteristics 

 of these observations: 



1. Both the respiratory volume and the respiratory rate decline 

 gradually, although occasionally after four or five hours a slight in- 

 crease may occur (cf. IX and XVIII). This increase is doubtless 

 explained by the fact that the respiratory centre is hypejexcitable 

 in decerebrate animals, so that the manipulation involved in with- 

 drawing blood from the femoral artery for analysis, or in cleaning the 

 femoral cannula of clots brings on a marked hyperpnœa which may 

 last for some minutes after the irritation is removed. 



2. The percentage of carbon dioxide in the alveolar air collected 

 in from one to two hours after decerebration (when all ether has dis- 

 appeared from the blood) varies between 3 • 3 and 3 • 9 in five of the 

 six cats of this group, and in numerous observations which we have 

 subsequently made this value has usually been found. Occasionally, 

 and for no evident reason, the percentage may be somewhat higher as 

 in experiments IX and XXVI. During the remainder of the period 

 of observation the percentage of alveolar COo either remains prac- 

 tically unchanged (XXVI) or it very gradually decreases. 



