56 DR. PAYNE, 



On Students' Microscopes. By J. F. Payne, M.B., B.Sc. 



The regalations of the College of Surgeons, now coming 

 into force, which require all medical students to become 

 practically acquainted with histology, and are giving so great 

 an impulse to this study in England, will impose upon many 

 students the necessity of providing themselves with a micro- 

 scope, and upon many teachers the responsibility of aiding 

 their choice. It is with the view of assisting both classes 

 that we have compiled the information contained in the fol- 

 lowing table. It is constructed entirely from data obligingly 

 furnished us by the makers themselves, who are, therefure, 

 solely responsible for the correctness of the statements made 

 therein.^ We do not, furthermore, undertake to recommend 

 any one of these instruments,- but no makers' names have 

 been admitted into the list except those of good repute ; while 

 the materials for a comparison are given by the table itself. 



We may perhaps, however, do a real service to the student 

 or beginner by pointing out what is the special importance 

 of each point in microscopical construction, on which we have 

 collected information. 



1. Height. — The size of a microscope is not a matter of 

 very great moment, and the convenience of a large or small 

 instrument depends in great measure upon the height of the 

 table, the seat, and so forth. But a small and portable 

 microscope often has advantages over a more ponderous one, 

 and the student of moderate means need not envy the pos- 

 sessor of a magnificent and sumptuous instrument. Length 

 of tube, however, be it remembered, increases, cceteris paribus, 

 the magnifying power. 



2. Diameter of tube. — The advantage of a large tube is thatit 

 gives, speaking generally, a larger field, but this difference 

 may be equalised by variation in the depth of the eye-pieces 

 or in the length of the tube. 



3. Coarse adjustment. — Practically there are but two forms 

 of this mechanism — the rack-work, with milled head, used iu 

 England, and the sliding tube, working by friction, which is 

 almost universal on the Continent. The latter is capable of 

 quite as delicate movement as the former, or even more deli- 



•^ Some makers, English and foreign, to whom we addressed a circular oa 

 this subject, have not responded to it. 



^ Valuable ini'orniation and advice on these subjects, with figures, is 

 contaiued in Prof. M. Foster's ' Report on Modern Microscopes,' published 

 by Hardwicke, Piccadilly, 1867. 



