CH. xxiv.] CHEYNE-STOKES RESPIRATION. 363 



in fatty degeneration of the heart. A typical tracing of the 

 condition is given above (fig. 324). It is seen to a slight 

 extent during ordinary sleep, and is very marked in hibernating 

 animals. 



Pembrey and Pitts have recently taken graphic records of this 



Fig. 325. Cheyne-Stokes respiration in hibernating dormouse. The line marked T gives 

 time in seconds. Line 1 gives the tracing of a respiratory group which occurred once 

 every 80 seconds, the temperature of the animal being 11 C. On warming the animal 

 to 13" C. the respiratory groups became more frequent (line 2). On warming the 

 animal still further it awakened, and breathing at first accompanied by shivering 

 became continuous. (Pembrey and Pitts.) 



condition in the hibernating dormouse, hedgehog, marmot, and 

 bat. In some cases the respiration has the typical Cheyne-Stokes 

 character, with a gradual waxing and waning (fig. 325). In 

 other cases periods of respiratory activity alternate with periods 

 of apnoea, but all the respiratory efforts are about equal in force. 

 (Biot's respiration.) 



The effect of Respiration on the Circulation. 



As the heart, the aorta, and pulmonary vessels are situated in 

 the air-tight thorax, they are exposed to a certain alteration of 

 pressure when the capacity of the latter is increased in inspira- 

 tion ; for although the expansion of the lungs tends to counter- 

 balance this increase of area, it never does so entirely, since part 

 of the pressure of the air which is drawn into the lungs through 

 the trachea is expended in overcoming their elasticity. The 

 amount thus used up increases as the lungs become more and 

 more expanded, so that the pressure inside the thorax during 

 inspiration, as far as the heart and great vessels are concerned, 

 never quite equals that outside, and at the conclusion of inspira- 

 tion is considerably less than the atmospheric pressure. It has 

 been ascertained that the amount of the pressure used up in the 



