104 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
1/5, 1/10, 1/20, i.e. one drop of serum to five of culture, and so on. 
Tlie tubes are examined after 2, 10, and 24 hours. The effect may be 
observed with the naked eye or through the Microscope. In the former 
case there is a deposit, the rest of the fluid being clear. Microscopical 
examination is used for control. 
The clinical value of the reaction, as tested on tuberculous and non- 
tuberculous persons, is reported as follows. Of the tuberculous cases, 
95 per cent, gave the reaction. In the lion-tuberculous cases, composed 
of (a) persons suffering from diseases other than tuberculosis, and ( b ) of 
presumably healthy persons, positive results were also obtained. In 
group ( a ) 33 per cent, were positive, and in group (/>) over 50 per cent. 
The inference drawn by the authors from these latter results is that 
they were evidence of latent tuberculosis. 
While admitting the difficulty of the technique, the authors are very 
confident as to the value, from a clinical point of view, of the tuberculous 
serum reaction as an aid to the diagnosis cf tuberculosis, especially in 
its earlier stages. 
(3) Cutting’, including 1 Imbedding 1 and Microtomes. 
Minot’s Automatic Precision Microtome. — The feed arrangement 
of this machine, as made by Messrs. Bausch and Lomb, is shown in 
fig. 20. It consists of a micrometer-screw, having pitch of 0*5 mm., 
which elevates the object-holder. The motion of the screw is trans- 
mitted to the object-holder through a triangular bar moving smoothly 
but firmly in a triangular channel, all lateral motion being eliminated 
by means of a wedge. The micrometer screw is provided at its lower 
extremity with two metal discs in contact, each having one hundred ser- 
rations, the acute angles of the upper disc pointing to the right, and 
Fig. 20. 
those of the lower to the left. The discs are revolved by means of the 
lever A, which is pivoted loosely on the axis of the micrometer-screw 
and provided with a pawl F. F is actuated by the small lever shown 
on the upper surface of A, so that when the actuating lever is thrown 
to the left, F engages the teeth of the upper disc, and motion of A to 
l>he right elevates the object. The spring ratchet E prevents any back- 
ward motion of the screw-head, and may be disengaged by means of the 
