RESPIRATION. 
205 
cles. In such a chest the lungs would be large, and the heart 
too, in all probability. To these should be added a fine, well-formed 
nostril, capable of dilating ; a large nasal fossa ; a capacious 
glottis and rima; a roomy wind pipe, and wide bronchial tubes, even 
to the air-cells ; the pulmonary artery and veins should be large, 
giving bulk to the lungs by bloodvessels and air-tubes, and not 
by interstitial cellular tissue. When the muscles of the body are 
in rapid motion, contracting in active succession, the blood flows 
through the veins of the body to the right side of the heart with 
increased velocity; a corresponding circulation is indispensable 
through the lungs, otherwise the right side of the heart must be 
distended with blood, and general venous congestion ensue. The 
increase of the blood’s motion through the veins is not depending 
so much upon an augmented force of the arteries as upon the 
action of the muscles. Give a lock of hay to a horse while he is 
being bled, and the motion of his jaws in eating will exhibit this 
phenomenon of the venous circulation. The respiration must in- 
crease in proportion to the circulation, for the blood, returning so 
much quicker and oftener to the heart, requires the lungs to be 
expanded in frequency corresponding with the action of the heart, 
in order to admit the blood through them. The blood, also, in 
the pulmonary arteries is the darkest and most venous of any in 
the body, and, of course, less fluid ; therefore it is essential to 
free respiration, that the pulmonary arteries should be large. 
There is less probability of congestion in the venous system within 
the lungs, for the blood in them, being in the highest degree 
of vitality and fluidity, will pass readily to the left side of the 
heart: but the bronchial tubes are required to be large, together 
with the air-cells, which, as I have shewn, are continuous forma- 
tions of the tubes ; and unless the atmospheric air can pass with 
facility to the air-cells, the pulmonary arteries, however equal to 
the performance of their prescribed function, would be unable 
to deliver the blood into the pulmonary veins. The most fatal 
congestion of blood that can possibly take place within the body, 
is that of the capillaries anastomosing over the air-cells, an event 
which must take place in degree proportionate with the obstruc- 
tion through the bronchial tubes. 
[To be continued.] 
D d 
VOL. XIV. 
