492 



PHYSIOLOGY 



CHAP. 



o 

 to 



XV. Just as the phenomenon of periodic cardiac rhythm 

 supplied the most direct argument in favour of the theory of the 



automatic functions of the heart, so that of 

 periodic respiration, or, at least, of certain 

 forms which it may assume, gives us direct 

 evidence of the automaticity of the respir- 

 atory centres. 



Periodic respiration, in its most classic 

 form, as first described by the English 

 physicians Cheyne and Stokes (1816-1854), 

 consists in an alternation of apnoea and 

 dyspnoea, of pauses and groups. Each group 

 of respirations shows a rise and successive 

 fall of intensity as well as frequency. The 

 first and last respirations are minimal or at 

 any rate quite shallow, while the central 

 respirations are deep or highly dyspnoeic. 

 Each group may reach a maximum of 20-30 

 respirations. The duration of the pauses 

 may be equal to, less than, or greater than 

 that of the groups ; but it is always above 

 40-50." 



These classical cases of periodic group- 

 ing of the respiratory acts are rare, and are 

 usually met with in serious disease of the 

 brain and heart, in the comatose period of 

 certain acute infections, and in the later 

 pre-agonic stage of various diseases. A 

 typical case of Cheyne-Stokes breathing is 

 that observed by Gibson (Fig. 228) in a man 

 suffering from chronic renal disease of the 

 kidneys. Less intense forms, on the con- 

 trary, in which the groups are represented 

 by a few respirations and the pauses give 

 intermittency for a few seconds (Fig. 229 A) 

 are tolerably frequent. The pauses may even 

 be absent, when the periodicity of breathing 

 is reduced to the rise and fall in intensity 

 of the respiratory acts, which succeed with 

 a certain rhythm, with no positive distinc- 

 tion of groups and pauses (Fig. 229, B). 



The most important thing to note in all 

 these forms of periodic respiration is that 

 the duration of the pauses is not in any 

 relation with the duration or number of the 

 respirations in the groups. Of great significance, again, is the fact 

 that the form of the groups may vary considerably ; sometimes 



