140 
Proceedings of Royal Society of Edinburgh . [sess. 
Additional Notes on the Rontgen X-Rays. 
By Dr John Macintyre, Glasgow. 
(Read May 4, 1896.) 
The first series of photographs thrown on the screen included 
the different parts of the human skeleton. The second series 
illustrated photographs of the soft tissues, such as the tongue, 
larynx, heart, and diaphragm, all from the living subject. The 
third series were taken with a view to reduction of the time in 
exposure. With the fourth is given a description of some experi- 
ments upon attempts to polarise the x-rays. 
The apparatus now most commonly employed was used in these 
experiments, viz., electricity (from the main), an induction coil 
giving a range of from 2 to 10 inch spark as recjuired, a Crooke’s 
tube having an aluminium cathodal disc, and a small plate of 
platinum for the positive pole. It is now known as the focus 
tube. Paget xxxxx-plates were used, as no particular advantage 
had been obtained from those specially prepared. The follow- 
ing points, amongst others, were found to be of great service 
in obtaining the best results : — Firstly, the current passing to the 
coil should be regulated according to the work to be done, and as 
little variation as possible should take place during the exposure. 
Primary batteries are not as satisfactory on account of this, and 
the best source is from the main. Lord Kelvin’s cell tester and 
ampere gauge were used in the experiments, and any variations 
in the current were regulated by means of a rheostat. Secondly, 
the Apps or other coil or transformer must give, with the present 
form of tube, six inches or even more of spark when the 
deeper tissues of the body, such as the spine, are being taken. 
Thirdly, the vacuum of the tube should be carefully regulated and 
tested to give the maximum results. In the best tubes this was 
done before taking them off the pump, and the most satisfactory 
test was the fluorescent screen. During the exposure the vacuum 
changes from time to time. This is indicated by an alteration of 
