RESPIRATION IN AIR 



87 



Fig. 50. Diagram of lungs and nitrogen uptake during a dive. Explanation 

 see text. (Scholander.) 



This is well brought out in the accompanying diagrams 

 (Fig. 50). The figure to the right illustrates the conditions 

 in the lungs of man breathing all the time in his helmet and 

 discharging air to the surface. The middle figures represent 

 the lung of a diving animal without a dead space (e.g., a 

 frog) at the surface and at the depths of 50 and 100 m, and the. 

 left-hand figures represent conditions when there is a dead 

 space having a volume 1/10 of the alveolar. At one hundred 

 meters all the air will be in the dead space and practically no 

 diffusion will take place. The curves give relative rates of 

 nitrogen uptake in the three cases. Quite recently Scho- 

 lander measured the lungs of fin whales of 22-25 meters 

 length (weighing probably about 70,000 kg). He found them 

 astonishingly small, holding only 1 J/£ to 2 cubic meters of air 

 when inflated to their maximum capacity. The trachea and 

 large bronchi dissected out would hold 150-200 liters or just 

 1/10 of the lung volume. These whales dive to depths of 300 

 m or more just after an inspiration. Laurie (1933), who 

 determined the gases dissolved in the blood and urine of a 

 number of blue and fin whales, found only slight supersatura- 

 tions with nitrogen. 



