SOME EXPERIMENTS UPON THE CURVED LINE OF 
DULNESS WITH PLEURITIC EFFUSION. 
By G-. M. Garland, M.D. 
It occurred to me that, if a fluid capable of could be injected 
into the pleural cavity of an animal, it would subsequently admit of 
exposure by dissection without disturbance of the mutual relation of 
lung and effusion, and thereby aid in interpreting the mysterious 
writing on the wall. 
With the kind assistance of Prof. H. P. Bowditch, I therefore began 
a series of experiments upon dogs, in his laboratory. The results 
obtained are not as complete and satisfactory as might be desired, but 
my apology is that ray time is too limited by other engagements for 
more complete investigation of the subject at present. 
We employed, in our experiments, several forms of glue and gela- 
tine, with chromate of potash as a hardening agent. Mutton suet 
and plaster of Paris were also used. The plaster of Paris gave the 
most satisfaction, but required great expedition in preparing and in- 
jecting it, as it set so quickly. It was mixed with water to a thick 
fluid consistence, and was then poured into a glass flask. This flask 
was arranged like a common wash-bottle. The air within it was con- 
densed by pressure from a rubber bulb, and this condensed air drove 
the fluid through a rubber tube connected with a canula in the dog’s 
side. 
One or»two of the. early experiments were aborted by the admission 
of air into the chest. The air allowed the lungs to collapse, and the 
injection assumed a hydrostatic level. 
To avoid this casualty, we chose a region where the canula could be 
boldly plunged through the chest-walls with least danger to the con- 
tained viscera. During full inspiration, the lungs occupy all the tho- 
racic space which is accessible to them. With expiration they con- 
tract, allowing the upper surface of the diaphragm to come in contact 
with the thoracic walls for some distance above its line of attachment. 
The canula, previously filled with water retained by a stop-cock, 
was plunged into this space between the ninth and tenth or the tenth 
and eleventh ribs in the axillary line. By inserting the finger through 
a small opening in the abdominal wall, the canula could be felt sliding 
along above the diaphragm. Its blunt end prevented accident, while, 
by its conical shape, it plugged the opening it made in passing through 
the muscles as it entered. 
Actual measurement of the amount injected each time was not made, 
inasmuch as this point could be of value only by comparison with a. 2 
thorax of fixed size. No two of the dogs were of the same size. The 
injections, therefore, are merely designated small, medium or large. 
Both dead and etherized living dogs were injected, with no dif- 
erence in the results. 
After allowing time for the setting, the skin of the animal was re- 
moved and the chest carefully percussed and outlined. (See Figures 
1 and 2.) The thorax was then opened, and the external line of dul- 
ness compared with the internal condition of affairs. 
Fig. 1. 
A B represents the simplest form of a 
curve. The effusion was small. 
A is opposite the eleventh rib on the back. 
Fig. 2. 
A B represents a curve of a somewhat 
larger effusion. The sudden rise of the 
curve, as it approached the sternum, was 
found to be partially due to a displacement 
of the heart by an injection in the opposite 
chest. 
The first point which our experiments demonstrated with regard to 
the mutual relation of lungs and effusions is that the resisting lung, 
rather than the encroaching fluid, is the chief moulding agent and fac- 
tor in determining the curve of dulness. In every instance, the lungs 
were practically unaltered in their gross anatomical shape, though of 
necessity compressed and occupying less room. 
The edges of the lungs, even, were not rolled in, as the moulds 
show for themselves. With forcible inflation of the lungs, these bor- 3 
ders act like wedges in cleaving the mould asunder. With the largest 
effusions, the lungs were approximated to the foetal condition of ate- 
lectasis, but with form intact. 
The first effect of a small effusion was to swing the lungs upon the 
large bronchi as hinges, upward and outward against the walls of the 
chest. Little or no fluid separated the lungs from the chest. It was 
only in cases of very large effusions, or of concurrent pneumo-thorax, 
that such separation occurred. 
Now the normal shape of the lower border of the lungs is a curve, 
with the lowest point behind, and rising as it advances forward. 
Hence, with a small effusion, the fluid being moulded to the lower 
surface and border of the lungs, as I have stated, the curve is simple 
and easily understood. [See figure.] Internally, between lung and 
heart, there seemed to be the point of least resistance to the fluid, 
which here found an escape by shooting up some distance. The actual 
pressure of the lung upon the surface of the fluid was sufficient to sus- 
tain a considerable column of the effusion in this region. 
Larger effusions, I have said, gradually crept in between chest-wall 
and lung. The curve must, therefore, be necessarily modified accord- 
ing to the depth of the intervening fluid, i. e., according to the relative 
ability of the different portions of the lung to resist lateral pressure 
and retain sufficient air to be resonant. This requires further investi- 
gation. Wintrichsays the curve is always highest behind, and thence 
declines to the median line in front. Dr. Ellis finds, however, that the 
line of dulness is lowest behind, rises on the sides, and sinks again in 
front. We found, with small and medium effusions in dogs, that the 
curve and lung were lowest behind. Thence the curve rose till it reach- 
ed the side, whence it proceeded, nearly horizontally, to the sternum. 
The borders of the lung overlap the effusion somewhat, i. e., wedge 
themselves in between chest and fluid. 
We made but one injection in the human body, and that in an infant 
a few days old, Unfortunately, we neglected to percuss the chest and 
note the curve, but the experiment was so far successful as to convince 
us that the principle of the lung moulding the effusion was the same 
in the child as in the dogs. 
I have insisted upon the lungs moulding the fluid, because it seems 
to me to be the most important factor. Ido not deny that the lungs 
may, in turn, be moulded by the effusion to some extent. It may be 
true with human lungs. It did not appear prominently with the dogs. 
I content myself with stating what we saw, without attempting any 
theory why, how, or with what force, the lungs oppose the effusion. I 
hope, at some future time, to have an opportunity to renew these ex- 
periments upon the human cadaver, and note the modifications of dif- 
ferent positions of the body upon the relation of the parts. Such 
observations might throw more light upon the conditions already seen 
and described. 
Incidentally to the injection of living dogs, we observed the follow- 
ing facts, which are of some interest. 
The dog’s breathing, which had been more or less diaphragmatic, be- 
came purely thoracic immediately on the injection of the fluid. On open- 
ing the abdomen after the injection, the diaphragm was found bagged 
down like a lobster net. With each act of inspiration, however, it could 
be felt to rise, being drawn upward by the separation of its points of 4 
attachment. The fluid could also be felt shifting1 its form and level with 
every act of respiration, thereby accommodating itself to each change 
in its containing vessel. That this movement of the diaphragm was 
purely a passive one, was demonstrated by grasping the muscle tight- 
ly between two fingers. It was perfectly limp and passive, devoid of 
muscular action. 
It was suggested that, in such an abnormal position, if the dia- 
phragm should by any means contract, it would, of necessity, act as 
an expiratory muscle rather than an inspiratory one, as it normally 
does. To demonstrate this point, we dissected out the phrenic nerve 
in the neck, and irritated it by electricity just above its entrance into 
the chest. 
Before injection, such irritation always produced a violent act of 
inspiration, followed either by a tonic spasm of the chest-muscles or 
by rapid irregular breathing during the continuance of the irritation. 
The same irritation of the nerve, after the injection, produced a vio- 
lent act of lt is evident that, with the muscle bagging 
down, contraction of its fibres must draw the dependent portion up- 
ward, and thus produce the phenomenon described. 
I conclude that, with effusions in the chest, the diaphragm must play 
a passive or contradictory part. 
Reprinted from the Boston Medical and Surgical Journal, September 17,1874,