Explanatory lettering of instrument: A, Huyghenian eye-piece; B, draw-tube graduated in millimetres; C, nose-piece; D, coarse adjustment; E, fine adjustment with millimetre screw; F, horse-shoe sliding stage, graduated with sliding bar in vertical and horizontal directions _for use as finder_; G, sub-stage rack and pinion screw; H and I, centring screws to sub-stage; J, carrier for condenser; K, mirror with movable arm supported on solid tripod foot.] The points of difference between this stand and the No. 1 model are that in the latter the fine adjustment carries the body only, and not the rack adjustment; the limb carrying both the body and the sub-stage is in one piece, giving, if possible, still greater rigidity; the rotation of the mechanical stage, which is divided on silver, is complete, and can be actuated by hand or rack work; it has a clamping screw and fine adjustment to sub-stage. _Baker’s Advanced Students’ Microscope_ (Fig. 89) may be described as a typical instrument, equally suitable for histological work and that of the advanced student. The intention of the maker in simplifying the adjustments and reducing the instrument in size, was to furnish a well-finished portable instrument at a moderate cost. This object has not been attained by supplying adjustments of second-rate quality, but by reducing their number to a minimum. [Illustration: Fig. 90.--The Mayall Removable Mechanical Stage.] The tripod foot of the “Nelson Model” is replaced by a claw foot, which is in effect a tripod, as it rests on three points; it has not the same wide spread, but this, far from being a disadvantage, renders the instrument more portable. It has rack and pinion coarse and Campbell differential screw fine adjustments, draw-tube graduated in m.m., extending to 180 m.m., eye-piece gauge the same as the Continental size, large square open stage to afford the greater freedom of manipulation; sliding bar with graduations on bar and stage, which suffice for registering any given field under a low power; holes are also drilled in the stage ready to receive an attachable mechanical stage should it be thought advisable to add one at a later date. The sub-stage is of the universal size with rack-work focussing, adjustment, and centring screws. [Illustration: Fig. 91.--Baker’s Model Histological Microscope. Dimensions.--Height when in vertical position and body racked down, 10-1/2′′; Height of stage, 4′′; Width of stage, 3-1/2′′; Height of optic axis when in horizontal position, 5-1/4′′; Spread of foot, 5-1/4′′; Diameter of mirrors, 1-5/8′′; Internal diameter of draw-tube, 11/12′′.] Messrs. Baker have recently introduced a similar instrument with swing-out sub-stage and adjustments for compensating for wear and tear of rack. The stage is also somewhat larger from back to front.