Observations on some Physical Properties of 
Protoplasm by Aid of Microdissection . 1 
BY 
WILLIAM SEIFRIZ. 
With one Figure in the Text. 
Introduction. 
E ARLY workers on protoplasm dealt entirely with living material. The 
advent of cytological technique with its methods of fixing and stain- 
ing opened up a new and fertile field of investigation, leading to the 
discovery of many heretofore hidden structures of the cell. But it was soon 
realized that many of these structures were the direct result of the fixing 
and staining of the material. Consequently, there is to-day a pronounced 
reaction against this method of making observations and an increasing 
sentiment in favour of observations on living material. 
Method. 
Morphological work on living protoplasm has been greatly stimulated 
by the recent introduction of an ingenious technique generally known as the 
microdissection method. The instrument used in this method is a modifi- 
cation of the Barber ( 2 ) pipette-holder and consists of two mechanical 
needle-holders, each capable of being moved in three directions. Glass 
needles with very sharp and rigid tips are used for dissecting the material, 
which is suspended in a water film on the under side of a cover-glass that 
constitutes the cover of a small moist-chamber under the microscope 
objective. A complete account of the method and the technique connected 
with it is given in an article by Chambers (10), to which the reader is 
referred. 
Precautions. 
The student of living protoplasm soon learns to appreciate the necessity 
of knowing as far as possible the exact condition of the material which he 
is studying. Indeed, the great problem in microdissection is to know when 
one is observing living, and when dying or dead protoplasm. While the 
structure and behaviour of dead protoplasm is in many instances highly 
1 Botanical Contribution from the Johns Hopkins University, No. '68. 
[Annals of Botany, Vol. XXXV. No. CXXXVIII. April, 1921.] 
