The Principles involved in the 
Construction of Spray- 
Tubes. 
BY 
ANDREW H. SMITH, M. D. 
REPRINTED PROM 
(Tile Yorfc .fttetncal .Journal 
for November 28, 1885. Reprinted from the New York Medical Journal 
for NovemberJtdfVsSIL' \ o v 
TIIE PRINCIPLES INVOLVED IN THE CON- 
STRUCTION OF SPRAY-TUBES* 
ANDREW II. D. 
The Bergsen, or, as it is more commonly called in this 
country, the Sass spray-tube, having practically superseded 
all other forms, it is to this that attention will be confined 
in this paper. 
The instrument consists essentially of two tubes placed 
one above the other, the upper one, which for brevity’s sake 
we will designate A, carrying compressed air or steam, 
while the lower one, which we will call F, supplies the fluid 
to be atomized. 
The free extremities of these tubes, greatly diminished 
in size, are so arranged in relation to each other that the 
stream of air issuing from A passes at a right angle across 
the tip of F. The action of the spray-tube depends upon 
the fact that air possesses a considerable degree of adhesive- 
ness, the different particles adhering to each other with no 
little tenacity. 
We are familiar with this property in viscid fluids and 
to a less degree in plain water, a drop of which can be 
drawn along a table by the finger, but we are not apt to 
* Read before the American Laryngological Association, June 25, 
1885. TI1E PRINCIPLES INVOLVED IN THE 
2 
think of it as belonging to the atmosphere or to gaseous 
bodies. Yet it is owing to the fact that the air or steam 
which escapes from A clings to and drags with it the air at 
the extremity of F that a vacuum is produced in F. Into 
this vacuum the fluid rises, and in its turn is caught by the 
current from A and dispersed in the form of spray. 
The greater the velocity of the air-jet escaping from'A, 
the greater will be the exhausting force exerted upofuF, 
and therefore the greater the efficiency of the atomizer. 
As the velocity of the stream of air is greatest at its center, 
where it is least retarded by friction, it follows that the axis 
of the opening of A should be exactly on a line with the 
extremity of F. 
The pressure being the same, the character of the spray 
will depend upon the relative size of the openings of A and 
F. Increasing the former permits more air to escape and 
gives a larger volume of spray with a greater carrying force 
and more power of penetration. Increasing the latter re- 
sults in a larger consumption of fluid, forming a coarser 
spray, and, if carried too far, results in dripping. 
A large opening for A with a small one for F gives a 
large body of very fine spray. A small opening for A with 
a large one for F gives a small body of coarsp spray. A 
successful application of spray to the throat or to the pos- CONSTRUCTION' OF SPRAY-TUBES. 
3 
terior nares often requires that it be effected as it were by 
surprise, and before there is time for reflex action of the 
muscles. Hence it is necessary that spray should be formed 
the instant the air-valve is opened ; for, if the arrival of the 
liquid at the point of F is delayed appreciably after air 
begins to issue from A, reflex contraction will have been 
excited by the contact of the air with the mucous surface* 
before any spray is produced. Now, no fluid will reach the 
point of F until all the air in F is exhausted, and the amount 
of air and the length of time required for its exhaustion 
will be in proportion to the length and the caliber of the 
tube. Hence these should be reduced to a minimum in 
spray-tubes intended for making quick applications. And, 
as there is nothing lost in any case by this construction, it 
may as well be made the general rule for all tubes. 
With a properly constructed spray-tube comparatively 
slight air-pressure will suffice for all purposes. Increase of 
pressure will compensate in a measure for defective con- 
struction of tubes, but it brings with it its own inconveni- 
ences, such as mechanical irritation of the surface to which 
the spray is applied, waste of compressing power, etc. 
The indications for the use of coarse or fine spray do 
not come within the scope of this paper, and will vary in 
accordance with the views of individual practitioners. The lew York Medical Journal, 
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