A Universal Microtome. 293 



becomes serious. In this microtome the screw is robust and of 

 large diameter, and the pitch i<5 1 mm., which is not too fine. 



The knives are ground in a macliine which gives a true 

 rectilinear movement to the grinding wheel, thus ensuring a 

 straight cutting edge. This is especially important when a slicing 

 cut is used for cutting sections. The back of the knife is also 

 straight and parallel to the cutting edge. The knife is in fact a 

 true prism. When this condition is fulfilled the cutting edge 

 remains straight when the knife is sharpened on the hone, and it 

 is far easier to produce a thoroughly satisfactory cutting edge. By 

 the special process of grinding adopted it is easy to make the 

 knives more or less hollow ground to suit different conditions. 



The microtome was designed and made by the Cambridge and 

 Paul Instrument Company.* In the design of the mechanism it 

 resembles the Eocking Microtome, which was designed and made 

 in the Cambridge Works. Many of the good features in this 

 instrument are due to the care and thought given to them by 

 members of the staff of the company. Tlie method of adjusting 

 the cutting angle of the knife is the design of Mr. C. C. Mason, 

 and the orientating object holder is due to Mr. J. L. Orchard. 



Summary. 



We believe that the advantages of this microtome may be 

 briefly summarized as follows : — 



1. The sections are fiat and are cut in a horizontal plane. 



2. Sections of any thickness in steps of 1 micron may be cut 

 between 2 and 35 microns. 



3. Owing to the rigid and geometric design of the instrument, 

 each section is of uniform thickness, and successive sections are of 

 equal thickness. 



4. Most of tlie cutting edge of the knife can be used so that 

 the knife requires the minimum amount of sharpening. 



5. The object holder can be readily adjusted in every direction. 



6. The instrument is robust. 



7. As there is little friction and the moving parts of the 

 instrument are light, it is possible to "follow through" with one's, 

 hand whilst the sections are being cut. 



* Patents have been applied for on this instrument. 



