ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
285 
tlie uppermost part of the micrometer screw. The screw e is then 
tightened up. 
With this instrument the knife may be used either in the cross or 
in the oblique position. The latter is shown in the illustration ; the 
object-holder is moved to either position by means of the screw g. 
Treatment and Manipulation of Paraffin-imbedded Sections.*— 
The principal advantage that celloidin possesses over paraffin is that it 
is more suitable for the manipulation of large sections. Prof. Strasser 
has laid himself out to devise means whereby this reproach may be 
Fig. 28. 
taken away from paraffin. This end may be attained by the adoption of 
the provisional slide (paper), by using a special form of microtome in 
which the sections are made to adhere to the provisional slide at the 
time of sectioning, and by leaving the sections on the provisional slide 
as long as possible. The provisional slide, which must necessarily be 
a roll of paper, is prepared either with wax or gum. In fig. 28 is shown 
the method of saturating the roll with Japanese wax. The illustration 
perfectly explains the method, and it is only necessary to point out that 
the roller K' is so far from the immersion tank that the wax is dry in 
the band before it reaches the roller. The rolls of gummed paper are 
made by passing the roll through a tank containing in solution gum 
arabic 50, glycerin 20, and water 100 parts, and then the band is dried 
by passing it through a tube heated underneath by a series of gas-jets 
(fig. 29). 
The sections are then stuck on by means of an adhesive made of 
collodion and castor oil. This procedure is facilitated by the use of 
Strasser’s “ Schnitt-Auf klebe ” microtome. After the bands or sections 
have been carefully numbered, they are covered with an adhesive com- 
posed of 2 parts collodion and 1 part castor oil, after which they are 
deposited in a turpentine bath, in order to dissolve the paraffin, and at 
* Zeitschr. f. Wiss. Mikr., vii. (1890) pp. 304-17 (2 figs.). 
