438 
8UMMAKY OF CURRENT RESEARCHES RELATING TO 
(3J Cutting, including Imbedding and Microtomes. 
A new Method of Using Celloidin for Serial Section Cutting.* — 
The following method is recommended by Mr. H. C. Bumpus as having 
several features which make it preferable to the ordinary methods of 
section-cutting : — It allows a perfect orientation ; the entire object is 
visible during the process of cutting ; yolk-bearing eggs offer no serious 
difficulty ; sections of large area and of unusual thinness are easily 
secured ; crimping and curling during the process of clearing are 
avoided and the sections may be readily arranged in series. 
The object is first stained in toto, dehydrated, infiltrated with thin, 
medium, and thick celloidin or collodion (Squibb’s flexible collodion 
rendered thick by evaporation is excellent) and finally placed in a paper 
tray filled with the thick collodion. In a few moments a film will 
form over the exposed surface of the collodion, when the paper tray 
with its contents is thrown into a jar of strong chloroform, in which, 
after a few hours, the collodion becomes quite hard. 
The tray is now taken from the chloroform, and, after the paper 
has been removed from the hardened block, the collodion with its 
enclosed object is placed in a vial of white oil of thyme, or some 
other similar oil. If the block of collodion is not large, in a few 
hours it will become as clear as glass, the stained object appearing 
as if suspended in a transparent fluid. 
For the process of orientation, the block of collodion may now be 
taken from the oil, placed in a watch-crystal, and, after covering with 
the oil of thyme, examined with a lens, or, if more desirable, with a 
compound Microscope. The side of the block that is to be attached 
to the object-holder of the microtome is now selected, wiped dry of 
the oil, and immersed for a moment in ether, and then smeared with 
thick collodion. The object-holder, a block of wood rather than cork, 
is smeared in the same way, and the two collodionized sui’faces are 
brought together. The holder and collodion block are now immersed 
for a few minutes in chloroform, or long enough for them to become 
firmly united. 
The preparation is now screwed between the jaws of the object- 
carrier of the microtome and covered, by means of a camel’s-hair brush, 
with oil of thyme. The microtome knife is flooded with the same oil. 
This oil, which takes the place of alcohol usually used, has the advan- 
tage, because of its lubricating property, of not only permitting thin 
sections to be cut, but its slow evaporation allows one to leave work 
at any time for minutes or even hours without the object being injured. 
After a few sections have been cut from the block of collodion, the 
relative position of the piano of the knife to the axis of the object 
can be definitely established. There is no difficulty in orienting small 
Arthropod embryos by simply examining the object and plane of cutting 
at this time with a compound Microscope ; the segments, appendages, 
and even nuclei are as clearly shown as if mounted in balsam. The 
object, satisfactorily oriented, is now cut and the sections at once 
transferred to the slides, covered with balsam and mounted, or, if they 
are not immediately needed, they may be kept indefinitely in a vial of 
the oil. 
* Amer. Nat., '"'i- <1892) pp. 80-1. 
