RESPIKATOKY MOVEMENTS OF THE GLOTTIS. 357 



In treating in detail of the function of respiration, it will 

 be convenient to make the following division of the subject: 



1. The mechanical phenomena of respiration ; or the pro- 

 cesses by which the fresh air is introduced into the lungs 

 (inspiration), and the vitiated air is expelled (expiration). 



2. The changes which the air undergoes in respiration. 



3. The changes which the blood undergoes in respiration. 



4. The relations of the consumption of oxygen and the 

 production of carbonic acid to the general process of nutri- 

 tion. 



5. The respiratory sense ; a want, on the part of the sys- 

 tem, which induces the respiratory acts (besoin de respirer). 



6. Cutaneous respiration. 

 T. Asphyxia. 



The study of these questions will be facilitated by a brief 

 consideration of some points in the anatomy of the respira- 

 tory organs. 



Physiological Anatomy of the Respiratory Organs. 



Passing backward from the mouth to the pharynx, two 

 openings present themselves : one, posteriorly, which leads to 

 the oesophagus, and one, anteriorly, the opening of the larynx, 

 which is the commencement of the passages devoted exclu- 

 sively to respiration. The construction of the oesophagus and 

 the air-tubes is entirely different. The oesophagus is flaccid, 

 and destined to receive and convey to the stomach the ar- 

 ticles of food which are introduced by the constrictions of the 

 muscles above. The trachea and its ramifications are exclu- 

 sively for the passage of air, which is taken in by a suction 

 force produced by the enlargement of the thorax. The act 

 of inhalation requires that the tubes should be kept open by 



ment. The perfection of organization in the higher animals seems to consist in 

 the multiplication of organs, for the more efficient performance of the various 

 functions. 



