312 The Microscope. 



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Acknowledgment. — To Dr. H. M. Westover, St. Joseph, Mo., 

 for several slides of Western fresh-water Diatoms, oak-leaf 

 fungus and blood of frog. The last mentioned is mounted in a 

 unique and pleasing way, two small covers being used side by 

 side, the stained corpuscles under one, and below the other the 

 unstained blood for comparison. 



NEV/S • FRPIA- 

 THEVv'ORKERS 



A NEW SYSTEM OF ERECTING AND LONG FOCUS OBJECTIVES. — M. 



L. Malassez,* after referring to the advantage of erect images 

 and long focal lengths, when delicate dissections have to be 

 made, exact measurements determined, etc., writes : — 



For these purposes we have already at our disposal the sim- 

 ple lens or the doublet, the Briicke lens, and the ordinary com- 

 pound microscope furnished with erecting apparatus. These 

 instruments are excellent in certain cases, but are certainly un- 

 satisfactory in man}' others. Thus, the simple lens and the 

 doublet do not give sufficiently strong magnifications with foci 

 sufficiently long, and, in making use of them, it is necessary to 

 bend over the object to be examined in a very uncomfortable 

 way. The Briicke lens possesses the advantage of having a 

 very long focus, but the magnification which it affords is not 

 very considerable. The microscope itself gives all the magnifi- 

 cation desired, but as soon as this becomes at all considerable 

 the focus is very short, and there is no room for manipulation. 



I have devised a new system of objectives which gives the 

 best results. Adapted to the ordinary microscope the objective 

 gives at once, without erecting apparatus, an erect image of the 

 object obtained. Its focus is very long, as long as could be 

 wished. One of them has a focus of seven centimetres, while it 

 gives a true magnification of thirty diameters with a No. 2 eye 

 piece of Verick, and a tube length of sixteen centimetres. I 

 have made some which had foci much longer, reckoned by 

 metres instead of centimetres. With these it was possible to 



*J. R. M. S., Ch. Arch, de Med. Exper. 



