MICROTOMY

                                                          MICROTOMY

Microtome

It is the device used for cutting thin section of around 5-7µ thickness. The type of microtome used for routine section cutting is rotary microtone
.
Rotary Microtome
The rotary microtone is used because a rotary-action of the hand wheel gives
the cutting movement . The block holder is mounted on a steel carriage which moves up and down and is advanced by a microtome screw. The knife is attached to the stage which can be moved  forward and backward. The angle of the knife is adjustable.


Advantages of rotary microtome are:
1)   Since it is heavier, it is mere-stable and it is ideal for cutting serial sections
2)    .It is ideal for cutting large number of sections from each block
3)   Since heavier and large knife is used , the chances of getting vibration are less, while cutting hard tissues.

KNIFE
 The type of knife used for routine section cutting is wedge-type and is made of carbon Steel. The knife should be sharpened regularly using automatic knife
sharpener or manually using the stone. This process is called Horning . Stone , glass, copper to which abrasive is added is used for honing. Stropping is the process of polishing an already fairly sharp edge. The stropes are made from hide from the rump of the horse.

Method of honing
1)    The knife handles and the knife back are attached to the knife .
2)   The edge of the knife nearer to the handle is called heel and the edge opposite is called the toe .
3)   A small quantity of light oiler soapy water is applied to the hone.
4)   While holding the knife, the handle should be between thumb and forefinger.
5)   The cutting edge should face away from the operator.
6)   The Knife is pushed forward diagonally from toe to heel.
7)   It is turned  over on its bask and brought back diagonally from heel to toe.
8)   The process is continued for minimum one hour depending upon the bluntness of the knife.


Stropping

 The only difference is, it is done on the Stropping leather and the cutting-edge is towards the operator.

Automatic knife sharpener
The knife is fixed to a clamp and it is held horizontally against the surface of a slowly rotating flat plate. After a predetermined number of strokes, the knife is turned over so that the opposite bevel is sharpened . A paste of abrasive with light oil is applies over the plate .


Cutting Technique
1)   Insert appropriate knife in the knife holder and screw it tightly in position. The clearance angel is  checked and it should be around 2'-6.
2)      Fix the block in the block holder.
3)       While fixing the block, the harder part-ef the tissues like skin margin, capsules should be on the upper sides .
4)      Adjust the block holder , so that the whole surface of the block is parallel to the knife edge
5)      Set the thickness at 15µ and trim the block until the whole section is exposed.
6)      Apply ice over the Section and start cutting at 5µ.
7)       Stop cutting, when you get some ribbon sections.
8)      Hold the forceps between the thumb-and-the-forefinger and middle finger. Hold the  edge of section with the-forceps. ,
9)      Slowly detach the Section from tiܘܵ knife with the brush.
10) The metal part should never come in contact with the knife as it causes nicks.
11) Float  the section Over-the-water bath the temperature of which is around 45°C (5*  to 10*C less than melting point of Wax used).
12) Remove the folds if any, with the forceps.
13) Hold the albumenized slide perpendicular to the section and touch the section gently. The section gets to the slide.
14)            Write the corresponding number on the slide with a diamond pencil.
15)  Keep the Section in a rack inside the incubator for 1 hr for fixation.
16)  The section should be positioned centrally on the slide.
17)    While cutting ensure that all the screws are tightened properly.


Albumenized slide

 Coat the slide slightly with albumin (equal amount of egg white and glycerol in
which a few crystals of thymol is added as preservative . Glycerol is used to increase viscosity and prevent complete drying. )



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