1895 - 96 .] I)r Macintyre on Bontgen X-Rays. 
143 
that side next the tube is so diffuse that it never appears on 
the plate. By this means one can select different hones of the 
body, and so we can photograph the mastoid cells, or even show 
the meningeal grooves or sutures on the inside of the parietal and 
occipital hones themselves. 
By carefully observing the above rules, and using an efficient 
apparatus, many of the soft tissues may easily he obtained. I have 
thus been able to photograph fasciae, muscle, cartilage as well 
as bone, and on the screen you will see photographs of the 
larynx through the side of the neck, showing also the tongue, 
hyoid hone, cartilage of the organ ; and in another picture the 
heart, showing the relationship to the ribs, the diaphragm below, 
and even a faint indication of the great vessels in the neck above. 
The time of exposure varied. In the earliest experiments expo- 
sures of half an hour were required, hut now many such photographs 
can he taken in the fraction of a second. Having noticed that the 
fluorescence of the tube was very much greater with a mercury 
interrupter than with the ordinary platinum spring, a series of 
experiments were carried out to determine the cause. It was 
noticed that although the current across the terminals, before pass- 
ing to the coil, should reach as high as 17 amperes, during the 
action of the interrupter it fell to 1 ampere. On the other hand, 
with the mercury interrupter, and the same current during the 
exposure, it reached as high as 7 amperes. It was clear, therefore, 
that a current was passing through the primary coil by this 
arrangement which would mean more powerfully induced currents 
in the secondary coil, and consequently greater effect in the vacuum 
tube. By this system one could measure the exposure, not by 
seconds, but by the number of flashes in the tube corresponding to 
each interruption in the coil. With one flash, the current register- 
ing 10 volts and 10 amperes, and the coil giving 6-inch spark, it is 
possible with a Paget xxxxx-plate to get a photograph of the bones 
of the hand, and 10 such flashes give an excellent negative, showing 
the intimate structures. What the actual time represented in 
these exposures may be it is impossible to say ; it must be an 
unknown fraction of a second. In any case, it is safe to say that 
the photograph is taken instantaneously. 
