THE PRODUCTION OF BRONCHIAL BREATHING 
IN CONSOLIDATION AND OTHER CON- 
DITIONS OF THE LUNGS. 
BY 
CHARLES CARY, M.D., 
OF BUFFALO, N. Y. 
FROM 
THE MEDICAL NEWS, 
July 2, 1892. [Reprinted from The Medical News, July 2, 1892.] 
THE PRODUCTION OF BRONCHIAL BREATHING 
IN CONSOLIDATION AND OTHER CON- 
DITIONS OF THE LUNGS.1 
By CHARLES CARY, M.D., 
OF BUFFALO, nTy. 
The title of this paper is perhaps subject to mis- 
conception. It includes the discussion of the physi- 
cal principles involved in the production of tubular 
breathing, and suggests that these same principles 
induce the broncho-vesicular and cavernous breath- 
ing, which differ from the first only in degree. 
There has been some little controversy upon this 
subject, limited, however, largely to those authors 
that have practical minds and a fancy for acoustics. 
Most of our modern text-books contain descriptions 
of the sound, and account for its production by 
quoting one of the few authorities that have written 
on tbe subject. The explanation offered by Laen- 
nec, and still held by some, was that the sound was 
produced by the vesicular murmur being cut off and 
the tubular or bronchial sound alone being audible. 
In the fourth edition of his work he expresses him- 
self as follows: "The sound observed in the larynx, 
trachea, and larger bronchial trunks is due to the 
1 Read at the meeting of the Association of American Physicians 
in Washington,' May 24, 25, 26, 1892. 2 
CARY, 
absence of that slight crepitation that accompanies 
the dilatation of the air-cells of the lungs, and the 
idea of a drier sound is suggested to us. It is strong 
in most parts of the neck. When the texture of the 
lungs becomes indurated or condensed from any 
cause, such as pleuritic effusion or the changes oc- 
casioned by a severe peripneumony or hymophysis, 
the vesicular respiration having then disappeared, or 
being much lessened, we can frequently perceive dis- 
tinctly the bronchial respiration,not only in the large, 
but even in the small ramifications of the bronchi. 
The cause of this bronchial respiration appears to 
me very obvious; in fact, when the air is prevented 
from penetrating the cells this is the only kind of 
respiration that can exist, and is louder and more 
distinct in proportion as the lung is more condensed 
and thereby becomes a better conductor of sound." 
Dance, a French authority of later date, adopts 
virtually the views of Laennec, and states in the 
Dictionnaire de Medecine, ou Repertoire Generale des 
Sciences Medicales, of 1833, that bronchial breathing 
is present when the air passes through the bronchial 
tubes without reaching the pulmonary cells. It 
produces in the ear a sensation of columns of air 
winding in the tubes of a certain caliber, without 
the sound of vesicular expansion; sometimes the 
sound is so intense as to make it seem that the 
patient's breath is passing through the stethoscope 
instead of through the bronchial passages. 
Skoda thought that the tubular breathing was the 
transmitted laryngeal sound intensified or otherwise 
altered through what he called consonance; but he 
does not use this word in its ordinary acoustic BRONCHIAL BREATHING. 
3 
sense, but explains that he applies it with the com- 
pound meaning of consonance and resonance, ap- 
plying the principles of the sounding-board to 
obtain the intensity that he suggests. He does not 
make his views clear, except so far as the principle 
is concerned. The following is a translation of what 
is written in his Abhandlung Uber Perkussion und 
Auskultation: Bronchial breathing can be higher, 
stronger, deeper, or weaker, or even just as high 
and as strong as laryngeal breathing, and is due 
to consonance in sound in the upper and lower por- 
tions of the air-passages; the difference in volume 
and pitch depends on the condition of the inner 
lining of the air-passages in admitting of the pro- 
duction of the consonant sounds. 
The most elaborate treatment of this subject that 
has come to my notice is found in Flint on the 
Respiratory Organs. Here Austin Flint devotes 
considerable space to this subject, and concludes by 
regarding bronchial respiration as " consisting of 
transmitted sounds that are produced within the 
trachea and primary bronchi, and probably also 
within the subdivisions of the latter, and are con- 
ducted by the air in the tubes and the consolidated 
lung to the ear of the auscultator. In what propor- 
tion they are due to the trachea and the larger 
bronchi exterior to the lungs, and to what extent 
sounds generated within the pulmonary bronchial 
subdivisions may be combined, are points not easily 
determined." 
Flint certainly had an analytic mind, and his 
description is the most satisfactory. More modern 
writers adopt this view without notable modification. 4 
CARY, 
Guttman devotes fair consideration to the opinions 
of others, but expresses his views as follows : " The 
bronchial respiratory murmur heard in disease is 
nothing more than the laryngeal sound carried with 
scarcely diminished intensity through consolidated 
lung-tissue." The views of R. C. M. Page and 
Vierordt are virtually the same. So also are those 
of S. S. Burt, excepting that the latter speaks of the 
sound as being transmitted through the bronchial 
tubes as through a speaking-tube, directly to the 
surface and ear of the auscultator. It will be ob- 
served that there is no great variety of opinion, and, 
without quoting at greater length, authorities are not 
fully satisfied with their own explanations, for they 
quite universally acknowledge differences of pitch 
over different regions in the same individual, and 
even contrast the laryngeal and tubular pitch, point- 
ing out differences that all will concede could not 
exist if the source of the sound were the same, for 
pitch cannot be altered by the medium of trans- 
mission, and, as Dr. Flint says, "there are circum- 
stances which give rise to variations in pitch which 
we do not understand, and that the sounds gener- 
ated within the trachea and bronchi as in conditions 
of health, will not suffice to explain the intensifica- 
tion of sound which sometimes characterizes bron- 
chial respiration in disease, nor the disparity in 
pitch which is observed." He further concludes 
that "other physical influences are doubtless in- 
volved which are not as yet satisfactorily explained. ' ' 
Dr. J. Bloodgood, of Chicago, published an 
article on this subject in i860 which has not 
received the consideration that it deserves, and my BRONCHIAL BREATHING. 
5 
attention was only called to it within the past few 
days. In this article it is claimed that hepatization 
is not necessary for the production of tubular 
breathing and that the normal lung-tissue offers a 
good medium for conducting sound, as demonstrated 
by the clearness with which sibilant rales are heard 
when the parenchyma is normal; that when a 
bronchus becomes temporarily blocked by viscid 
mucus a clear tubular sound is at once detected, and 
this disappears when the secretion is coughed up; 
during the time it is heard the lungs are normal. 
Dr. Bloodgood argues from this that the air in its 
passage downward is diverted into many tubes the 
aggregate capacity of which is much greater than 
that of the trachea and bronchi; that it therefore 
rushes more and more slowly the more deeply it 
penetrates; that should a small bronchus become 
plugged at a little distance from its origin, or lead 
to cells filled with inflammatory product, it would 
furnish a cavity analogous to the Pandean pipe, 
and yield a tone determined by its size; that if it were 
located high up in the lungs, where the air has the 
greatest velocity, it would be intense, but if located 
in the lower lobes the sound would not be induced, 
or if present the intensity would be diminished. 
His argument is based upon false anatomic grounds, 
and he does not accord the transmitted laryngo- 
tracheal sound its place. 
I began, about three years ago, a line of work 
and experimentation having the great charm called 
original work, which always acts as a wholesome 
spur, and after eighteen months of time it developed 
most successful results; but in that time I also made 6 
CARY, 
the discovery that my undertaking was not new, 
though I had succeeded without the knowledge that 
the ground had already been staked out by others. 
The work referred to is the making of casts of the 
air passages, and for that purpose I used an alloy 
composed of-tin, 4 parts, lead 8, bismuth 15, and 
cadmium 3. This alloy softens at 6o° Centigrade, 
and fuses at 65°. 
I do not know how my castings may compare with 
those made by others whose opportunities may have 
been better than mine, and who may have purused 
their work for a longer period than I did, for I have 
never seen any of the kind; my object is only 
to illustrate the basis of the explanation here advanced 
as to the causes that contribute to the production 
of the sound that we all term tubular or bronchial 
breathing. The castings are made from healthy 
lungs. These should be procured as soon after 
death as possible, and the cast is formed by pouring 
the alloy of low fusion into the trachea and allowing 
it to penetrate as far as possible into the tubes and 
vesicles before it chills and consolidates. It hardens 
almost immediately into a solder-like form, and the 
lung is then macerated in caustic soda, and eaten 
off, leaving the casting, representing what must be 
the exact caliber and shape of the air-passages, as 
far as the metal has penetrated, without burning 
or destroying the pulmonary tissue. I need not 
remind you that success does not attend each at- 
tempt, that the degree of heat, the pressure and the 
presence of moisture will modify the result and act 
as factors in the frequent failures, and determine 
the degree of success. In most instances castings BRONCHIAL BREATHING. 
7 
of the larger bronchial tubes were obtained; in some, 
of the most minute tubular subdivisions; and, in a 
few, of the surrounding vesicles. 
Whenever the vesicular castings were obtained 
the tubes were of course hidden from view. The 
castings were also not complete throughout the lung, 
and were often unavoidably broken off in the pre- 
paration, even by their own weight. Human lungs 
do not prove good specimens unless procured from 
subjects dying from hemorrhage and after a short 
illness, as the mucus always present debars the pos- 
sibility of a perfect cast. The preparations were 
made from adult and infant human lungs, and the 
lungs of sheep, calves, dogs and rabbits. In many 
cases the alloy was poured into the trachea while 
the lungs were still in situ. 
It is not within the province of this paper to dis- 
cuss the anatomy of the lungs or to point out the 
errors that exist in some of our best descriptive 
Anatomies ; but I particularly invite attention to the 
method of division or branching of the bronchial 
tubes, which quite uniformly takes place at about 
the same angle, and uniformly by bifurcation, and 
that the air only reaches the air-cells after passing 
through a long route and varying in its course at 
the different points of bifurcation. Furthermore, 
at these points the bronchial tube possesses a sharp 
edge, which acts as a prow to cut the column of air 
at the bifurcation. This cutting edge is described 
in Sappey's Descriptive Anatomy, and he says that 
on a level with each division one sees in the cavity 
of the bronchial tubes a spur or prow to cut the 
column of inspired air. If the bronchi are given off 8 
CARY, 
at an acute angle this spur is very pronounced and 
very sharp. In collapsed lungs the bronchi are 
naturally much diminished in size, and this cutting 
edge is not very apparent, as it is not thrown out in 
relief; but in consolidated lungs, as in pneumonia, 
it is readily seen. I am confident that bronchial 
breathing is a mixed sound, composed of laryngo- 
tracheal and cavernous elements, the laryngo-tracheal 
sound being transmitted through the bronchial 
tubes by the air in their cavities, and thence com- 
municated to the consolidated or compressed lung, 
to the chest-wall, and heard by the auscultator, 
diminished in intensity according to the lack of 
transmitting power of the different media through 
which it has to pass; that added to this sound in 
proportions differing under different circumstances, 
but often predominating in volume, is a tubular 
blow that is produced by the air rushing over the 
open and cavernous mouth of a patulous bronchus 
that leads to a lung not receiving its quantum of 
inrushing air. 
Now, bearing in mind the cavities represented by 
these bronchial tubes, either of the first, second or 
third magnitude, the air-cutting edge referred to by 
Sappey, at the point of bifurcation, I believe we 
have the explanation needed for variations in pitch, as 
well as one of the contributing elements in inducing 
tubular breathing, and, perchance, the same tubular 
blow will be induced, whether the air is passing in 
or out of the lungs. 
This point can be demonstrated by five figures of 
a purely conventional character, to illustrate how 
tubular breathing can be produced in the higher BRONCHIAL BREATHING. 
9 
grades of pneumonia with consolidation; in 
pleurisy, with effusion, when the lung is in contact 
with the chest-wall; in necrosis, with a cavity; and 
how, when produced, it could not be heard in cases 
of effusion, if fluid intervened between the lung and 
the chest-wall. In all of these cases it is apparent 
that over areas in which tubular breathing is heard 
there is diminished or suppressed vesicular expan- 
sion. Under these circumstances it can hardly be 
questioned that, in order to reach other portions of 
the lungs, the air rushes by and over the bronchus 
leading to the diseased portion, to fill the air-vesi- 
cles that do expand, and that at the point of de- 
parture the cutting edge described by Sappey must 
produce a reverberation, engendering a sound 
analogous to that which would be produced by 
blowing over a test-tube; and its pitch will depend 
upon the length and caliber of this bronchus ; this 
is the additional sound that, for lack of a better 
term, I have called the bronchial blow. If the rush 
of air to other parts of the lungs is rapid, the inten- 
sity of this sound will be augmented. If the size of 
the tube be small and shallow, its pitch will be 
raised; if large and deep, the pitch relatively low- 
ered ; but in any case, higher than a laryngo- 
tracheal sound, except in conditions of disease of 
the larynx, in which case its pitch might be raised 
much above the normal. When this sound is in- 
tense, as we find it in the rapid breathing of acute 
pneumonia, or extensive effusion, with the lung 
pressed or bound to the thoracic wall, it contributes 
largely to the sounds heard, thus raising the pitch 
and augmenting the intensity. Should rapid 10 
CARY, 
breathing subside in the cases named, or should 
secretion obstruct the mouth of the tube, or fill its 
cavity, then the intensity of this element would 
diminish, or the sound entirely disappear. The 
pitch of this blowing sound is determined, as has 
just been stated, by acoustic laws and depends 
upon the length of the bronchus and its caliber at 
its point of departure. The principle is susceptible 
of ready demonstration, with apparatus to be found 
in any of our offices. Blowing over a small test- 
tube will yield a sound of a certain pitch ; on filling 
the tube partially with water, the pitch will be 
raised ; a long, narrow tube will yield a low-pitched 
sound ; a flask may be treated in the same way to 
illustrate the reverberation in a cavity. This ex- 
periment may serve to explain how, after a short 
lapse of time, both pitch and intensity of sound 
may be altered in conditions of consolidation by 
the presence of secretion in the tubes. I would 
further offer as an explanation of the exaggeration 
of the tubular element heard over cavities, particu- 
larly when they are near the surface, that the 
intensity is very much augmented by the proximity 
of the sound to the ear of the auscultator, and this 
rule applies equally to all physical sounds, and the 
more remote from the point of its production, the 
less audible it becomes; it is for this reason that 
sounds are sometimes limited to very small areas, 
particularly when the medium of transmission is 
poor. Again, sounds produced externally to the 
larynx cannot be heard with distinctness, and those 
which are most distinctly heard are produced at the 
periphery of the air-passages, or near the ear of the BRONCHIAL BREATHING. 
11 
auscultator; labial sounds, such as chirping and 
whistling, are only heard as transmitted by the 
external air; they are never intense, whereas any 
artificial means that produce a rush of air in the 
respiratory tract nearer the ear are markedly exag- 
gerated, as, for instance, the expiratory "puffs," 
produced in this way; whisperings are intensified 
in like manner; the intensity of sound at different 
periods of respiration depends upon the same law. 
I do not think it would be possible to state what 
proportion of the sound is attributable to the differ- 
ent elements that go to make it up, for I am con- 
vinced that the proportion varies notably with 
different degrees of consolidation and under vary- 
ing conditions, the discussion of which would be 
foreign to my purpose here. It seems to me that 
the reason why this explanation has not been offered 
before is because the size of the tubes has been very 
much underrated by those who are in the habit of 
making physical examinations ; commonly when ex- 
amined the lungs are collapsed and the bronchi are 
diminished in size, but the castings show that there 
are fully sixty tubes in the human lung capable of 
inducing a bronchial, blowing sound, while several 
bronchial casts in distended lungs have a diameter 
of about half an inch in the clear; these latter 
would certainly yield a large volume of sound. 
Before closing I would not be understood as 
saying that the larynx does not play a role, and a 
very important one, in determining the pitch and 
quality of bronchial breathing, for I have experi- 
mented upon some of the lower animals, inducing 
pulmonary consolidation, and with an opening into 12 
BRONCHIAL BREATHING. 
the trachea I have been able to cut off the laryngeal 
sound at will ; from this experiment, although it 
was not complete, for I found it difficult to produce 
pneumonia in a dog at will, I was convinced that 
the larynx, as well as the trachea and the bronchial 
blow, are the three elements that, in the aggre- 
gate, induce the sound that has been the subject 
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