660 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
(3) Cutting-, including- Imbedding and Microtomes. 
Virchow’s Cutter for Dissection of Membranous Preparations.*— 
This apparatus of Herr Hans Virchow, of Berlin, is the result of diffi- 
culties often experienced by the author in getting truly cut sections with 
scalpel or scissors through embryo layers and such like objects. In 
addition to accomplishing the purpose of cutting to any desired orien- 
tation (so that serial sections may be afterwards made if desired), it 
permits the dissection of a preparation into parts without damage. 
This apparatus (fig. 163) consists of four parts, — knife, glass plate, 
knife-holder, and frame. 
(1) Knife. — The knife M takes the form of a blade 30 mm. in length 
and 20 mm. high. The lower side bears the edge, and the upper is 
fastened to the knife-holder by two screws Sr. The holes for the screws 
are not circular but slit-shaped, being prolonged perpendicularly, so that 
in tightening the screws the knife is capable of a slight up and down ad- 
justment. For it is necessary that the knife should be most accurately 
set, so that in the downstroke the edge should exactly reach the plate ; 
in this way the object will be cut through without damage to the edge. 
The two screws J, inserted in the crossbar B, serve to complete this 
adjustment ; they press on the knife-back, and are used to depress the 
knife, if necessary, after the screws Sr have been tightened. 
Fig. 163. 
(2) The Plate G consists of a rectangular piece of plate-glass, 
9 cm. long by 6 cm. broad, and bears three finely scored lines which 
serve for orientation of the preparation. Two of these lines s are parallel, 
* Zeitschr. f. wiss. Mikr., xvi. (1899) pp. 295-9 (1 fig.). 
