ORGANS OF RESPIRATION. 



6. The IH.HUS, (Figure 11.) are very elastic, spongy organs, 

 contained in the cavity of the chest, and formed by the union of 

 a great number of membranous vesicles resembling little cells, 

 which generally communicate one with another. Into these 

 vesicles is introduced the external air: when it penetrates their 

 cavities, it distends them and thus augments the entire volume of 

 the lung, which happens in inspiration; on the contrary, when 

 the lungs are emptied of the air which distends them, their volume 

 diminishes, as happens in expiration. 



7. The lungs communicate with the external air by a long 

 c^nal which is terminated by the mouth and nose. 



8. The air to reach these organs, passes through the nasal fossa3, 

 or nostrils, or through the mouth into the pharynx, then enters into 



the larynx, descends along the 

 trachea, or windpipe, and is 

 distributed to the pulmonary 

 cells by other canals or tubes, 

 called bronchia3, (Fig. 11.) 



9. The nasal fossa?, and the 

 mouth terminate internally in 

 the pharynx, or gullet, so that 

 the supply of air necessary 



, < for respiration may reach this 

 n cavity by either route. 



10. At the bottom of the 



Fig. 11 



...mi 



pharynx, or swallow, we find 

 an opening called the glottis, 

 which leads into the larynx, 

 and permits the air to enter 

 therein. 



11. The larynx is a short 

 tube of considerable diameter, 

 situated at the superior and 

 anterior part of the neck, and which contributes to the production 

 of the voice.^ . 



"^Explanation of Fig. 11. The lungs and trachea ; on the left side of the cut, 

 the lung is represented entire (p,) and on the right, are the canals which convey 

 uir into the interior of all the cells of this organ, 6, the mouth, mi, the lowei 

 ,aw, A,the hyoid bone, I, the larynx, I, the trachea, or windpipe, br. bron 

 chiai, br\ ramuscles or small branches of the bronchia, ;), the lungs. 



6. What are the lungs? 



7. How do the lungs communicate with the external air ? 



8. Flow does the air reach the lungs ? 



9. How do the nostrils terminate internally ? 



10. To what part does the glottis lead ? 



11. What is the larynx? 



