COLLECTING, PRESERVING AND APPLIANCES 33 



magnifying- about 10 — 15 diameters is indispensable ; and 

 for dissecting one must bave a simple microscope. 



Nothing elaborate is required, and indeed a perfectly 

 practical dissecting stand can be improvised from a cigar-box 

 and a scrap of mirror, with a bent wire to hold the lens ; 

 but, in choosing an instrument, be careful to select one with 

 broad, gently-sloping wings on which to rest the hands. It 

 is a mistake to fit it with expensive lenses, as all such, work 

 very close to the object in proportion to their power, and 

 room to manipulate is of more importance than excellence 

 of definition. Two simple plano-convex lenses of lin. 

 and ^in. focus, are all that is required for the actual dis- 

 secting, but one modern achromatic lens of high power may 

 be added, not for working under, but for the purpose of 

 examining the preparation at intervals. 



As regards the compound microscope, the practitioner 

 in the tropics requires something that he can conveniently 

 take to the bedside of the patient for the diagnosis of 

 malaria. 



As myself the designer of a folding microscope, I can 

 with the better grace say, that none of them appear to me 

 sufficiently rigid for use with high powers ; and therefore 

 prefer a portable, but not a folding stand, and for the last 

 year have been using that catalogued by Leitz. 



Messrs. Smith and Beck also showed me a somewhat 

 similar and equally excellent instrument. Both these stands 

 have sufficient weight and rigidity for use with the highest 

 powers. For diagnostic purposes the 3mm. Zeiss dry 

 apochromatic is a most useful lens, but for critical work 

 on the parasite the highest powers of the best makers are 

 required, though there is no need to spend additional money 

 on lenses of exceptional angular aperture. 



I give these details, which may seem somewhat out of 

 place here, as one is often asked what should be recommen- 

 ded as the most convenient outfit for the tropical medical 

 practitioner. 



Entire larvse are best mounted as microscopic objects in 

 4 per cent, formol solution, to which a very little glycerine 

 has been added, but I should doubt if such mounts would 

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