A. External Respiration . . . . . . .513 



I. The Structure of the Respiratory Mechanism . . 513 



II. Physiology — 



1. Physical Considerations . . . . .515 



2. Passage of Air into and out of the Lungs . . 516 



i. Movements of Respiration .... 516 



Inspiration . . . . .516 



Expiration . . . . .521 



Special Respiratory Movements . . . 522 



ii. Amount of Air Respired .... 522 



iii. Interchange of Air by Diffusion . . . 523 



iv. Breath Sounds ..... 524 



V. Rhythm of Respiration .... 525 



vi. Nervous Control of Respiration . . . 526 



1. Chemical Regulation .... 527 



2. Reflex Regulation .... 532 



3. Interaction of Circulation and Respiration . . 535 



A. Influence of Respiration on Circulation . . 535 



B. Influence of the Heart on Respiration . . 536 



4. Interchange between the Air and the Blood , . 537 



i. Effects of Respiration on the Air Breathed . 537 



ii. Effects of Respiration on the Blood . . 538 



iii. The Causes of the Respiratory Exchange . . 539 



1. Partial Pressure of Gases in the Air Vesicles . 539 



2. Partial Pressure of Gases in the Blood . 541 



B, Intermediate Respiration ...... 545 



C. Internal Respiration ...... 547 



