26 
January 267H, 1871. 
MICROSCOPICAL MEETING.—THE USE OF THE 
‘POLARISCOPE IN THE DETERMINATION OF 
STRUCTURE. 
Mr. Szwett, who had proposed the subject for the evening,—the 
use of the Polariscope in the determination of Structure,—remarked 
that with most microscopists the Polariscope was merely a toy to show 
pretty objects, whereas he believed it ought to be applied to the de- 
velopment of structure. Having enquired of Mr. Curties respecting 
Hislop’s selenite stage, he was informed that Mr. Ackland had contrived 
a very simple one, which he thought he could borrow ; but he had done 
better : for he had induced Mr. Ackland to come to exhibit and 
explain his selenite stage. 
Mr. Wonror considered that alarge number of microscopists used 
the Polariscope as a scientific instrument in making out structures, 
Mr. AcKLAND was sure the majority used it as a toy; he might 
say 15 out of 20. Scarcely any had a selenite plate, with the axis 
marked. He did not think he had been asked to mark the axis, 
once in 20 years. 
Mr. Wonror thought that a large amount of work was done by 
microscopists without using the selenite at all, and then only with 
objects possessing slight depolarizing power. They would all feel 
obliged by Mr. Ackland’s pointing out the advantages of marking the 
axis. 
Mr. AckiaND said, if the axis of the selenite film was marked, it 
was possible to determine the tension of any object, especially, say, in 
the examination of muscular fibre, where it pointed out the direction 
of the tension, The Germans, who were generally in advance of us in 
minute anatomy, always used marked selenites. One of the few 
persons he knew using one in London was Mr. Stewart, of St. Bar- 
tholomew’s Hospital. 
Selenite films, giving the various tints, blue, green, yellow, red, 
and purple were commonly used ; but all must have noticed, when 
examining an object which did not fill the field of view, that the colour 
of the background did not harmonize with the colours of the object, 
a 
