82 BIOLOGY AND ITS MAKERS 
Nierstrasz from the specimen in possession of the University 
of Utrecht. The instrument consists of a double copper plate 
in which the circular lens is inserted, and an object-holder— 
represented in the right-hand lower figure as thrown to one 
Fic. 19.—LEEUWENHOEK’S Microscope. 
9 
Natural size. From Photographs by Professor Nierstrasz, of Utrecht. 
side. By a vertical screw the object could be elevated or 
depressed, and by a transverse screw it could be brought 
nearer or removed farther from the lens, and thus be brought 
into focus. 
Fig. 20a shows the way in which the microscope was 
