ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
587 
hollow stand for protection’s sake. It is completely skeltered from 
direct hand-touch. It is turned by means of an endless screw E (figs 
09 and 100) which gears into the toothed wheel S, working on the flange 
of the screw, and carries the usual micrometer knob. By means of this 
arrangement two conditions are satisfied : the fine adjustment is slowed 
in the most desirable way without the necessity of requiring from the 
micrometer-screw too fine a motion, and the position of the endless 
screw, so firm and safe in the handle-like stand, renders even rough 
mechanical operations entirely without effect on the fine adjustment. 
In order to avoid injury to the micrometer-screw when the slide F is 
at its extreme highest or lowest position, a special protection arrange- 
ment, limiting the play of the endless screw, is contrived for the fine 
adjustment. As is seen from fig. 100, the endless screw E engages 
another toothed wheel S 2 which is a nut working on a vertical screw. 
This nut S 2 comes into contact with the upper or lower surface of the 
chamber containing it before the fine adjustment slide F reaches the 
end of its travel, thus preventing strain on that part of the mechanism. 
Messter’s Bacteria Microscope.* — The makers of this instrument 
claim that its specially advantageous construction almost entirely removes 
troubles arising from loss of time (1) in changes of eye-pieces and 
objectives ; (2) in tedious coarse adjustment for various powers ; (3) in 
laborious picking out of very minute objects with strong magnifications. 
Investigations can therefore be made, even by a tyro, more quickly, 
accurately, and conveniently, with this instrument than with any other. 
It is specially recommended to physicians for diagnosis of urine and 
sputum. The figure (101) shows clearly the arrangement of the eye- 
pieces and objectives with their revolvers ; and the fitting of these is so 
perfect that the image is always adjusted for every nine magnifications. 
[Thus apparently no coarse adjustment is required. — Ed.] An improved 
central micromillimetre-screw secures the fine adjustment ; and a lever 
under the micrometer-screw effects a raising or lowering of the tube 
without change of adjustment, which is very convenient in the applica- 
tion of thick-ringed slides, or in the rotation of the objective revolver. 
Messter's Compressorium Microscope. f — This is specially designed 
for the easy and certain discovery of trichin ee and other objects. 
By pressing down the lever G (fig. 102), the pressure of the com- 
pressorium II on the glass plates and J 2 is released, and the table- 
screw L is diawn back to its fullest extent. This screw withdraws the 
runners on which rest the glass plates, and these last receive between 
them the slice of meat to be examined. When the object is ready the 
compressorium is again brought into play, and inspection is made by 
transmitted light with the weak objective. The outside corner of the 
field is at first under the Microscope ; then, by rotation of the mother- 
screw K, the front line of numbered squares are brought one by one 
into view T ; L is now turned until the first of the next row is in sight, 
and, by reversing the mother-screw, the whole of the squares in the 
second line are inspected ; thus in time the whole of the field is examined. 
When once found the revolver brings the high power into use. As the 
* Messter’s Catalogue, p. 12. 
t Cat. cit., p 21. 
