RESPIRATION 



107 



abundant extensity, as has just been seen and as is shown graphically 

 in the diagram. A layer of air 200 square meters in size separated 

 from a like extent of rapidly moving blood by only two layers of highly 



FIG. 58 



--- 2 



Diagram to show the relations of the air-chambers to the lungs in a carinate bird (e. g., any 

 American bird). The lungs are the shaded portion of the picture: 1, clavicular air-sacs; 2, 

 cervical sacs; 3, anterior, and 4, posterior diaphragmatic sacs; 5, abdominal sac; h, air sac in the 

 humerus. (B. Haller.) 



FIG. 59 



Two alveoli from the lung of a goose. The right-hand picture shows the air-spaces injected 

 (black), while the left-hand view is that of the injected arterioles. (F. E. Schulze.) 



