524 RESPIRATION 



together, the, first respirations of each group always begin small and 

 gradually increase in amplitude until their maxim am has been reached. 

 Subsequent to this point they again decrease slowly to complete stop- 

 page. The intervening respiratory standstills may last only a few 

 seconds or a longer time, say, 30-40 seconds. As Eyster 1 has shown, 

 these variations in the respirations are accompanied by rhythmic 

 changes in the blood pressure, a rise occurring most generally toward 

 the end of the apneic phase, at which time the oxygen tension of 

 the alveolar air is greatly diminished. The succeeding respirations, 

 therefore, would be incited by a lack in oxygen. Pembrey, 2 .on the 

 other hand, advocates the view that the apneic phase is caused by a 

 diminution in the carbon dioxid tension which leaves the respiratory 

 center temporarily without its normal stimulus. At all events, it is 

 possible to remove this condition for a time by the administration of 

 either oxygen or carbon dioxid. The former tends to heighten the 



FIG. 261. TRACING SHOWING THE CHEYNE-STOKES FORM OF RESPIRATION. (Hill.) 



irritability of the respiratory center, whereas the latter stimulates it 

 until it again discharges its impulses. 



A similar type of respiration is frequently observed during sleep 

 and in meningitis, in which disease it constitutes an unfavorable 

 prognostic sign. It is known as Biot's respiration and consists of 

 rapid short breathing which is interrupted by pauses lasting from 

 several seconds to half a minute. 



Hyperpnea. This condition is characterized by a moderate in- 

 crease in the respiratory rate and amplitude. It is attributed as a 

 rule to a diminution of the oxygen and an increase of the carbon dioxid 

 occurring in the course of heightened muscular activity. Besides the 

 carbon dioxid, it is entirely 'probable that other fatigue substances are 

 present which act as powerful exciting agents of the respiratory center. 

 It is also possible to augment the respiratory activity in an indirect 

 manner by stimulating the receptors for touch, pain and temperature. 

 A reaction of this kind is usually experienced upon tactile impressions, 

 as well as upon the immersion of the body in water of 32 C. or in 

 water charged with carbonic acid gas. It can also be produced by 



1 Jour, of Exp. Med., viii, 1906, 565. 



2 Jour, of Path, and Bact., xii, 1908, 258. 



