332 MANUAL OF PHYSIOLOGY. 



movements, and, consequently, the effort of standing produces a 

 more frequent respiration than is found in the recumbent posture. 

 Emotions variously affect the rate and rhythm of the inspiration 

 and expiration {e.g., sighing); and, finally, morbid conditions, 

 implicating the lungs, usually cause a greater frequency of respi- 

 ration, sometimes attaining a rate of as many as 60-70 respira- 

 tions per minute. 



The thorax is enlarged in all directions during inspiration, 

 the motion being usually referred to the vertical, transverse and 

 antero-posterior diameters respectively. 



The vertical diameter is increased by the descent of the lateral 

 parts of the diaphragm, and the slight elevation of the parts 

 about the apex. 



The lateral diameter is widened by the side droop of the ribs 

 being lessened ; each rib is rotated upon the line uniting its 

 extremities, and at the same time is moved upward and outward. 



The antero-posterior diameter is enlarged by the general ele- 

 vation of the ribs and sternum, the anterior extremities of the 

 ribs, being drawn up from their general downward incline, push 

 the sternum forward. 



The movements of the diaphragm depress the abdominal vis- 

 cera lying beneath it, and thereby distend the elastic abdominal 

 wall and compress the gases contained in the intestines. Thus, 

 the diaphragmatic movements cause a rhythmical heaving of the 

 abdomen. Kespiration depending chiefly on the action of this 

 one muscle is, therefore, spoken of as abdominal respiration. On 

 the other hand, when the ribs are the chief cause of expansion 

 of the upper parts of the chest, it is called thoracic or costal 

 respiration. 



These two types of respiratory movements may be imitated 

 voluntarily, and are variously combined in different individuals 

 during ordinary respiration, and in the same individual under 

 different circumstances. 



In men the general character of the ordinary quiet respiration 

 is abdominal, the movement of the thorax being insignificant in 

 comparison with that of the abdomen. 



In women the reverse is the case; the abdominal movements 



