76 THE AMERICAN MONTHLY [March, 



Section-Cutting. 



The tissues being fixed, hai^dened, and imbedded, it is neces- 

 sary to cut tliem into tliin sections with a certain area. There are 

 many processes and instruments by which to attain this. . . . We 

 advise the use of Weiss's Enghsli razor. . . . When a good razor 

 has been obtained most carefully, keep it away from a manufac- 

 turer or a cutler. We make this remark whenever we see a razor 

 put into their hands, for on its return it will be exceedingly bril- 

 liant, but it will not cut. This is singular, but easily jjroved by 

 experience. It is as important that the histologist should know 

 how to sharpen a razor as to know how to use the microscope. 

 Buy a razor strop and a good stone with a fine grain. Pass the 

 razor back and forth over the stone moistened with neat's-foot oil, 

 applying the blade lightly upon the stone, and always holding the 

 G.iS<gt forward (toujours le tranchant en avant) . When well sharp- 

 ened pass it several times over the leather and wash in alcohol to 

 remove the oil. . . . 



Free-Hand Cutting.— This demands a certain manual skill, 

 but it is of great instrumental simplicity, as it requires only one 

 instrument, the razor. . . . Take a stick of elder pith as large as 

 possible and remove the outer layers, which are filled with silica. 

 Cut a furrow in it longitudinally. Gently separate the edges of 

 the cleft, and between them place the tissue imbedded in gum. 

 The elasticity of the pith will hold the object in the cleft. Take 

 the pith between the thumb and finger of the left hand, and the 

 razor in the right hand. Dip the blade in alcohol and while wet 

 boldly cut through the object. ... It is well to support the razor 

 on the thumb nail. The following method by Ranvier for the 

 study of nerves will make the operation easier : The piece, well 

 sponged ofl" with bibulous paper, is placed in a little hollow made 

 in the pith. Then pour into the cavity a mixture of pure wax 

 and oil, raised to a temperature not to exceed the melting point. 

 "• When the mixture is cold, the first cut having leveled the surface 

 of the three bodies (pith, wax and oil mixture, object) to make 

 the second, with the razor depress the surface of the pith so as to 

 elevate as small a quantity as possible of the wax and of the ob- 

 ject ; cut by a single stroke made more certain as the razor rests on 

 a guiding surface. The pith thus used takes the place of a micro- 

 tome." Whatever plan may be adopted the sections float in the 

 alcohol on the blade, and may be removed by dipping the razor 

 in water. 



Cutting with the Hand (or Ranvier) Microtome. — A long 

 apprenticeship is needed to cut good sections by the foregoing 

 method, and there are a great number of microtomes intended to 

 make the procedure entirely mechanical. Ranvier's is the simplest 

 of these. "It is formed of a hollow cylinder, having at one end 

 a flat plate and at the other a micrometric screw, which raises a 

 piston within the cylinder," To make thin sections by this micro- 

 tome, take rods of elder pith freed from the silicious layer, and 



