FKEQUENCY AND CHARACTER OF RESPIRATORY MOVEMENTS 475 



Respirations 



in a 

 minute 



New-born 62 



0- 1 year 44 



5-15 years 26 



15-20 years 20 



20-25 years 18. 7 



25-30 years 15 



30-50 years 17 



The fact that the respiratory frequency varies in accordance with 

 the intensity of the metabolism may be proved in several ways. Thus 

 it is readily noticed that muscular exercise and glandular activity 

 increase it, while sleep diminishes it. 1 A heightened respiratory 

 activity is usually associated with rises in the temperature of the body 

 or of the surrounding air (heat dyspnea). A similar effect is pro- 

 duced by increases in the barometric pressure and in the carbon di- 

 oxid content of the inspired air. The frequency of respiration and 

 the size of the animal preserve an indirect relationship to one another, 

 because the smaller animals possess a more extensive body-surface 

 in relation to their mass than the larger ones, and hence, suffer a 

 much greater loss of body-heat. This greater dissipation necessitates 

 a more rapid production of heat, i.e., a more active metabolism. The 

 latter is invariably characterized by a greater respiratory frequency. 2 



The wide differences noted in different species are made apparent by 

 the following table: 



Horse 6-10 



Ox 10-15 



Sheep 12-20 



Dog 15-25 



Pig 15-20 



Man 16-24 



Cat 20-30 



Pigeon 30 



Rabbit 50-60 



Sparrow 90 



Guinea-pig 100-150 



Rat 100-200 



The rhythm of respiration is also disturbed by emotions and during 

 the production of sounds, such as are used in speaking. In health 

 a fairly constant ratio of 1 : 4 is maintained between the rate of respira- 

 tion and that of the heart. It is also true that this ratio is frequently 

 retained even under pathological conditions, because the respiratory 

 and cardiac activities are subject to practically the same influences 

 and react toward them in an almost identical manner. 



The Changes in the Position of the Lungs. The expansion of the 

 lungs gives rise to a change in their volume and hence, also in their 



1 Chait, Dissertation, Zurich, 1907, Dohrn, Zeitschr. fur Geburtsh., xxxii, 

 1895, 25, and Recklinghausen, Pfluger's Archiv, Ixii, 1896, 451. 



2 Johanson, Skand. Archiv fur Physiol., 1895, 20. 



