328 MANUAL OF PHYSIOLOGY. 



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 

 are slight when compared with those of the upper part of the 

 thorax. This difference is only well marked during quiet uncon- 

 scious breathing ; any forced or voluntary respiratory effort 

 changes the typical character of man's breathing, and the costal 

 movements become more prominent. In a forced deep inspira- 

 tion the upper part of the chest shows the greatest increase in 

 the antero-posterior diameter in both sexes. 



This difference in type between male and female respiratory 

 movements has been ascribed to different causes. The most com- 

 mon of these is the change brought about by the costume ordi- 

 narily adopted by females. This can hardly be an adequate 

 explanation of the phenomenon, for we find the same type exist- 

 ing when the tight garments are removed, and it is apparent in 

 those who have never been constricted by tight clothing, and 

 even in cases where no clothing at all has been used, as amongst 

 the inhabitants of hot countries ; so that, though the corset may 

 induce an exaggeration of the costal respiration, by constricting 

 the lower ribs and interfering with the action of the diaphragm, 

 it would not seem sufficiently to account for the normal physio- 

 logical costal type of breathing found in women. 



The occasional distension of the abdomen during pregnancy 

 has also been assigned as a cause of the female type of breathing. 

 That this type of breathing should be transmitted from our female 

 ancestors is possible, but it is very unlikely that pregnancy is the 

 sole agency in producing it, since in childhood the costal type is 

 marked in both sexes. It is probable that the abdominal breath- 

 ing of the male is also acquired and increased by hereditary 

 transmission, and is really due to the gradual increase in the 

 development of the muscles of the upper extremity in males, 

 causing a greater fixedness of the upper ribs from which they 

 take origin. 



