ON A NEW CLASS AND DEMONSTRATING MICROSCOPE. Br Henry Lawson, M.D., M.E.C.P.E., Professor of Histology in St. Mary's Hospital, London. The microscope whose two forms are represented in figures 1 and 2 is one which lias recently been constructed, at my suggestion, by Mr. Charles Collins, the Optician of Great Tichfield Street ; and may, I think, be found useful by those engaged in teaching microscopic anatomy. The old method of lecturing upon diagrams, and exhibiting specimens under the microscope after lecture,has these two serious objections: ls?,a large number of microscopes must be employed; and, 2ndly, the students, in clustering round the instrument, push and jostle each other, and thus earnest workers, anxious to observe, are prevented giving the necessary attention to the

object

MSKii#

by the idle sheep" which, unfortunately,

under observation

"black

every class possesses. I find it necessary, therefore, to hand the micros-

cope during lecture to the student nearest to me, who in his turn passes Fig. 1. it to bis neighbour, and thus, while T am describing a particular tissue, the students are enabled to follow the account which I give

Fier. 2. Fig.

that, on the average, I exhibit eight or nine specimens in each lecture, and therefore the system of using hand microscopes seems tome to work very well, and to result in driving ideas into a greater number of heads than could be done on the old plan. This idea of using hand microscopes is by no means ori ginal, as far as I am concerned. It was tried some years since, and with success, by Dr. Lionel Beale. "What I wish to convey to your readers is that I have devised a method by which the ordinary microscopes, which are employed in actual work in a medical school, may be easily converted into demonstrating microscopes. The instrument figured above may therefore fairly be styled a convertible microscope." In figure 1 it is seen as used in research, and in figure 2 as employed in demonstrating to a class. Its peculiarity is this?the leg of the instrument, the part intervening between the stage and the solid circular foot, is really double, being composed of a solid brass stem which slides within a tube. This tube is fixed by a knuckle-joint to the circular foot, and carries the mirror. When the microscope is wanted for demonstrative purposes, it is simply drawn out from the tube, thus leaving the foot and mirror behind, and a tube bearing a small lamp filled with colza oil is slid over the leg. The microscope then has the form represented in figure 2. This instrument is supplied with two good objectives : an inch and a a double nose-piece ; its coarse quarter inch, which are fixed in adjustment is telescopic, the fine adjustment being regulated by In this form, with plain the usual screw. stage and single eye-piece, it is sold by Mr. Collins at the extremely moderate price of four pounds ten shillings, and is, I think it will be admitted them.

"

I find

THE INDIAN MEDICAL GAZETTE.

56 by

those who examine it, the cheapest microscope yet made. nothing of the toy about it; its magnifying powers are

There is

not above 300 diameters, and it is provided with but a single mirror; but it is, nevertheless, an instrument which may be used with advantage by the student, and which, in schools, may be made,like Goldsmith's chest of drawers," a double debt to pay." When not We have several of them in use at St. Mary's. employed in the theatre, they are arranged as in figure 1, and are then used

by

the students in the

Histological Laboratory.

[Maech 2,

1868.