THE RESPIRATORY SYSTEM. 373 
Facial and laryngeal respiration is best seen in such animals 
as the rabbit, and it is this condition which is approximated 
in disordered states in man—in fact, when from any cause in- 
spiration is very labored (asthma, diphtheria, etc.). 
In man and most mammals, unlike the frog, the glottic 
opening is never entirely closed during any part of the respira- 
tory act, though it undergoes a rhythmical change. of size, 
widening during inspiration and narrowing during expiration, 
in accordance with the action of the muscles attached to the 
arytenoid cartilages, the action of which may be studied in 
man by means of the laryngoscope. 
The abdominal muscles have a powerful rhythmical action 
during forced respiration, though whether they function dur- 
ing ordinary quiet breathing is undetermined; if at all, prob- 
ably but slightly. Though the removal of the external inter- 
costals in the dog and some other animals reveals the fact that 
the internal intercostals contract alternately with the dia- 
phragm, it must not be regarded as absolutely certain that such 
is their action when their companion muscles are present, for 
Nature has more ways than one of accomplishing the same pur- 
pose—a fact that seems often to be forgotten in reasoning from 
experiments. This result, however, carries some weight with it. 
Types of Respiration.—There are among mammals two princi- 
pal types of breathing recognizable—the costal (thoracic) and 
abdominal—according as the movements of the chest or the 
abdomen are the more pronounced. 
In the civilized white woman, even in the female child, the 
upper thorax takes a larger share in respiration than in the 
male sex. This has been explained, on the one hand, as being 
due to artificial influences, modes of dress, and their inherited 
effects; and on the other to natural ones, the crowding of the 
respiratory organs, owing to the contents of the pelvic and 
abdominal cavities encroaching on the thorax, in consequence 
of the enlargement of the uterus during pregnancy. It has, 
however, been maintained recently that an examination of 
pure-blooded Indian girls does not show the features of respira- 
tion just noticed ‘as characteristic of the breathing of white 
fernales, the inference from which is obvious. But, again, it is 
to be remembered that the Indian and other women retaining 
primitive habits possess a power of adaptation to the demands 
of the pregnant condition no longer shown by white women. 
Thoracic breathing in females is probably the result of several 
co-operating causes, of which usage in dress is one. 
