322 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



The heating apparatus is represented in fig. 41 ; and by slightly raising 

 or lowering the flame, the temperature can be regulated and kept constant 

 within half a degree Centigrade. 



(2) Eye-pieces and Objectives. 



Malassez' New Micrometer Eye-piece.* — M. Malassez, after de- 

 scribing the defects of many micrometer eye-pieces, relates his attempts 

 to remedy them : — 



(i.) His first type has three concentric tubes sliding smoothly in 

 one another (fig. 42). The middle one bears at its two extremities the 

 two eye-piece lenses ; it is the ocular proper. This tube has also several 



Fig. 42. 



Fig. 43. 



Fig. 44. 



lateral openings ; one very wide, admitting the micrometer slide ; a 

 second, on the same side and higher, near the upper lens ; and two 

 others vertically elongated, vis-a-vis, by whose means the interior tube 

 can be operated. This inner tube carries the micrometer, and is 

 sensibly less than the middle tube. Near its lower end it has a wide 

 window for admitting the micrometer, which is actually placed on a 

 diaphragm, and is retained in position on a circular rim and clipped by 

 little springs. This inner tube also has two small milled projections, 

 which penetrate the two vertical openings of the median tube, and allow 

 of up-and-down adjustment. The projections are no thicker than the 

 metal, but the milling allows a good grip, and the movement is easily 

 done. The other window of the median tube exposes a mark on the 

 innermost tube, which slides past a millimetre scale. The exterior 

 tube is intended to close all the windows of the median tube. 



When the focus has once been obtained, it is only necessary to note 

 what reading on the millimetre scale corresponds to the reading on the 

 tube, and the precise arrangement can be at any time recovered. 



(ii.) This type differs much from the last, and is an ordinary ocular, 

 whose upper lens-mount bears on its lower face the arrangement for 

 raising or lowering the micrometer slip. This arrangement (fig. 43) con- 



* Arch. Anat. Micr., 1900, pp. 429-35 (3 figs.). 



