BLOOD SYSTEM. 



365 



Fig. 247. — Diagrams showing the different kinds 

 of respiration : A, pure thoracic ; B, pure ab- 

 dominal ; C, mixed. The dotted lines repre- 

 sent the expanded condition. 



These two kinds of respiration may be considered, 

 and indeed may be used separately. Fig. 247, A, is 

 a diagram repre- 

 senting pure tho- 

 racic, and Fig. 

 247, B, pure ab- 

 dominal respira- 

 tion. But the two 

 are usually com- 

 bined, and the 

 whole body cavity 

 enlarges and con- 

 tracts as in Fig. 

 247, C. In labored 

 respiration the 

 thoracic predominates; in quiet respiration, and espe- 

 cially in sleep, the abdominal predominates. In men 

 there is a slight predominance of the abdominal, in 

 women of the thoracic. 



Thus, then, the zVzspiratory muscles are the internal 

 intercostals and the diaphragm; the expiratory mus- 

 cles are the internal intercostals and the abdominal 

 muscles. 



Coughing and sneezing are violent convulsive actions 

 of the <?.xpiratory muscles. It is a little singular that in 

 popular literature, and even in many school text-books 

 of physiology, these should be so often referred to con- 

 vulsive action of the diaphragm. Of course, this is im- 

 possible since the diaphragm is an z'wspiratory muscle, 

 and coughing and sneezing are expulsive efforts. Every- 

 body knows that constant excessive coughing will pro- 

 duce soreness of the abdominal muscles. Hiccough is a 

 spasmodic action of the diaphragm, and laughter a spas- 

 modic alternate action of the inspiratory and expiratory 

 muscles, with the latter predominating. 



