RESPIRATION 4O$ 



more than a few millimeters. In labored respirations these movements are 

 naturally increased in extent. The irregular movements of the membranes 

 occasioned by the unskilful use of the laryngoscope, especially with nervous 

 patients, are not to be regarded as strictly physiologic. The respiratory 

 -pace in quiet breathing is an isosceles triangle, with a length of 20 mm. and 

 , width at the base of 15.5 mm. with an area of 155 mm. 



Respiratory Types. Observation of the respiratory movements in the 

 two sexes shows that while the enlargement of the thoracic cavity is accom- 

 plished both by the descent of the diaphragm (as shown by the protrusion of 

 the abdomen) and the elevation of the thoracic walls, the former movement 

 preponderates in the male, the latter in the female, giving rise to what has been 

 termed in the one case the diaphragmatic or abdominal type and in the 

 other the thoracic or costal type of respiration. The cause of this greater 

 mobility and activity of the thorax in the female has been a subject of much 

 discussion. It has been attributed, on the one hand, to the necessity for a 

 physiologic adjustment between respiration and child-bearing, and therefore 

 a specific sex peculiarity; on the other hand, it has been attributed to per- 

 sistent constriction of the waist, in consequence of which the full play of the 

 diaphragm is prevented and the burden of inspiration is thrown on the thora- 

 cic muscles. It has been assumed that if inspiration were confined in women 

 to the diaphragm, there would arise in the latter stages of gestation such an 

 increase in intra-abdominal pressure that not only would respiratory ex- 

 changes be interfered with, but fetal life might be unfavorably influenced, 

 if not endangered. Modern investigations have not confirmed this assump- 

 tion, but, on the contrary, have corroborated the view that the preponderance 

 of thoracic movement is due to the influences of dress restrictions, for with 

 their removal the so-called costal type of breathing entirely disappears. 

 While gestation may lead to a greater activity of the thorax, this is but tem- 

 porary, for with its termination there is a return to the diaphragmatic type 

 of breathing. 



Number of Respirations per Minute. The number of respirations 

 which occur in a unit of time varies with a variety of conditions, the most 

 important of which is age. The results of the observations of Quetelet on 

 this point, which are generally accepted, are as follows: 



Age. Respirations per Minute. Age. Respirations per Minute. 



o- i year 44 20-25 years 18.7 



5 years 26 25-30 years 15.0 



i 5 - 2 oyears 20 30-50 years 17.0 



From these observations it may be assumed that the average number of 

 respirations in the adult is eighteen per minute, though varying from moment 

 to moment from sixteen to twenty. During sleep, however, the respiratory 

 movements often diminish in number as much as 30 per cent., at the san 

 time diminishing in depth. 



Rhythm. Each respiratory act takes place normally m a regular 

 methodic manner, each event occurring in a definite sequence and occupy- 

 ing the same relative period of time. This rhythm however, is not mfa 

 quently temporarily disturbed by emotions, volitional acts, muscle acti 

 phonation, changes in the composition of the blood, etc.; with the removal 

 of these disturbing factors, the respiratory mechanism soon ret 

 normal condition. 



