286 A Simple Object-Finder for Students'

nature, and is not open to the objections which may be urged against the best of our modem " classifications." I t had the great advantage that as it was not based on science, truly or falsely so called, so it need not vary with the ever shifting sands of imperfect medical knowledge. I t served to detect disease, to diagnose it, to treat it when curable; and to permanently separate the diseased from the healthy, when incurability was demonstrated.

In conclusion, I may refer the reader to the articles LErROSY and M~a)IcI~, in Smith's Dictionary of tl~e Bible (1863); and among the numerous works therein noted I may name Shapter's Mediea Sacra (1834), and Bartholini (Thorn.) De Morbis Biblicis Miscellanea. This.last curious treatise is to be found in Ugolini's Thesaurus Antiquitatum Sacrarum (Vol .XXX., p. 1,521), published in folio, at Venice, in 1765, and is classed Hag. W,, 1.30, in the library T.C.D.

ART. X I I I . - - A Simple Object-Finder for Students' Microscopes. By THOMAS POWSLL, L.R.C.S.I., Enniskean, County Cork ; late Assistant-Surgeon H.M. Bombay Army; formerly Lecturer on Practical Anatomy in the Original (now Ledwieh) School Medicine, &c., &c.

DURING the last year I have been using a simple addition to the stage of my microscope, which acts as a most efficient object-finder, ] find it most accurate with all powers up to the sLinch object-glass.

This diagram shows the arrangement, and represents the stage of a student's microscope as made by Smith and Beck. In order to use this finder with a microscope, it is necessary for the object- carrier to be well fitted, and move easily and accurately in the vertical direction. The object-carriers of all good students' microscopes are, I believe, sufficiently well fitted, and I find that of Messrs. Smith and Beck answers perfectly.

The finding line (A) is a fine black engraved line marked on the stage of the microscope, near its right margin, vertical to the object carrier, and parallel to its plane of movement at about one inch and two-tenths from the centre. A small piece of paper, or of gummed label (B) three-fourths of an inch long, and one-fourth of an inch wide, attached to the upper surface of the slide, where it overlaps

Microsco~ves. By MR. POWEI,L. 287

the finding-line, completes this simple apparatus. I t is used thus : - An object being in the field to which it is desirous to recur. The

A o .,o.~176

\0/l__ J . . . . . . . . . . . B

i

s i

Mr. Powell's Object-l~inder.

observer moves his head to the right, so as to get a view of the findlng-line and label; he then with a pen makes a line on the label in apparent continuation of the finding-llne. In order to find that object at any future time it is only necessary to place the slide on the stage, and adjust the microscope so that the object would not pass through the field unobserved, then push the object-carrier fully down, placing the slide so that the line on the label is again in apparent continuation with the finding-llne, when by moving the object-carrler upward the object will be seen to enter the field.

In marking the line on the 1,~bel it is necessary to observe whether the pen is "s lghted" with one or both eyes, and to use either habitually, otherwise an inaccuracy in replacing the slide will result, which, being magnified by the power of the microscope, will prove material.

I t has occurred to me that the finding-line might be marked on the object-carrier, or on a small plate attached to it. I have tried it so placed, but whether from habit or not, I find the line on the stage the most convenient. If, however, the object-carrier was imperfectly fitted I think it would be better to place the line upon it.