RESPIRATION. 377 



dioxid are greater both absolutely and relatively. Thus, in a boy of 

 nine and a half years with a weight of 22 kilograms it was found that 

 in twenty-four hours there was a discharge of carbon dioxid amounting 

 to 488 grams, or 0.92 gram per kilo per hour, and in man with a 

 weight of 65.5 kilograms there was a discharge of 804.72 grams, or 0.51 

 gram per kilo per hour. 



MODIFICATION OF RESPIRATORY RHYTHM. 



The character of the respiratory movements is materially modified 

 by a change in the quantitative and qualitative composition of the 

 air and blood as well as by changes of a pathologic nature of the re- 

 spiratory apparatus itself. 



Eupnea. So long as the air retains its normal composition and 

 the respiratory mechanism its structural integrity, so long do the 

 respiratory movements exhibit a normal rhythm and frequency. 

 To the condition of easy tranquil breathing: the terrr^eupnea\s given. 

 In this coliditionthe'pCTCentll^es oi oxygen and carbon dioxrd in the 

 blood are such as to favor at least the rhythmic discharge of nerve 

 impulses to the respiratory muscles, of sufficient energy and frequency 

 for the maintenance of normal respiration. 



Hyperpnea. The normal rate of the respiratory movements is 

 increased by a rise in body-temperature, by_active exercise, and by 

 emotional states. Whatever the cause, the increase in rate and prob- 

 ably in depth is termed hyperpnea. 



Febrile states characterized by a rise in the temperature of the 

 blood increase considerably the respiratory activity. This is due in 

 all probability to a warming of the respiratory center, in consequence 

 of which its excitability is heightened; for surrounding the carotid 

 arteries with warm tubes and heating the blood on its way to the 

 medulla has the same effect. It is also possible, however, that the 

 high temperature of febrile conditions may interfere with the absorb- 

 ing power of hemoglobin, and thus by diminishing the quantity of 

 oxygen absorbed lead to more frequent respirations. To the hy- 

 perpnea induced by heat the term thermo-polypnea is frequently 

 given. 



Muscle activity, especially if it is violent and indulged in by 

 those unaccustomed to exercise, is generally followed by increased 

 rate and depth of breathing, and not infrequently it is attended with 

 such extreme difficulty that the condition approximates that of 

 dyspnea. This condition is attributed to the production and dis- 

 charge into the blood of unknown waste products which act as 

 irritants to the respiratory center and thus increase its activity. 

 As they apparently can not be isolated and their chemic nature deter- 

 mined, it is presumable that they are speedily oxidized or reduced 

 in the blood. Experiment has shown that the increase of carbon 



