RESPIRATION. 



341 



tissues. This water-test of the lungs is one of the medico-legal tests 

 applied to ascertain whether a child found dead was "stillborn" or 

 was a victim of infanticide. 



The substance of the lung is of a light, porous, spongy texture, 

 crepitating when handled because of the air contained in its tissue. 

 Lung-tissue is very highly elastic; it completely collapses when re- 

 moved from the thorax or if the thoracic walls be punctured so as to 

 admit air from the outside into the pleural cavity. 



Fig. 113. Mold of a Terminal Bronchus and a Group of Air-cells 

 Moderately Distended by Injection, from the Human Subject. ( ROBIN.) 

 (From Mills's "Animal Physiology," copyright, 1889, by D. Appleton 

 and Company.) 



In color the lungs are pinkish at birth, but of a mottled slate 



)lor in adult life. The dark-colored patches are produced by the 



xresence of carbonaceous material that has been inhaled and deposited 



ithin the areolar tissue near the surface of the organ. The carbon 



irticles are absorbed by the lymphatics, being carried into the lym- 



mtic openings by the leucocytes. 



Bronchi. In structure the bronchi resemble the trachea. In the 

 )ronchi, however, there are unstriped muscular fibers forming the 



