RESPIRATION. 



347 



and short elevators of the ribs and the external intercostals. All of 

 these muscles by their contraction directly affect the expansion of the 

 chest. The diaphragm is, par excellence, the muscle of inspiration; 

 the others do not contract very extensively except for the needs of 

 labored or forced inspiration. The scaleni are concerned in women 

 to aid inspiration of the superior costal type, which is peculiar to 

 the sex. 



When a person is devoid of strong emotions or is not engaged 



Fig. 118. Schema of Respiratory Mechanism in Inspiration. 

 (LAULANIE.) (See explanation, Fig. 119.) 



work or exercise, the breathing is quiet and regular. It is then 

 lid to be of the ordinary type and is principally diaphragmatic in 

 iracter. 



When, however, the breathing is extraordinary in type, various 

 )ther muscles are called into action. 



The size of the chest-cavity is increased in (a) its vertical 

 liameter as well as in (b) its lateral and antero-posterior diameters. 

 ie diameters are ascertained by means of calipers. 



From the student's study of anatomy he knows that the dia- 

 phragm, when at rest and in a state of relaxation, presents the gen- 



