Micrometry

microorganisms are microscopic objects that are visible only with the help of a microscope. micrometry refers to the measurement of dimensions of the desired microorganisms. ocular micrometer and stage micrometer.

1. MICROMETRY Sachu Elsa Mathew B.A.M College Thuruthicad

2. Microorganisms are microscopic objects that are visible only with the help of a microscope. Sometimes it is necessary to measure its dimensions for its identification process. But determination of the size of a microorganism is not an easy process.

3. Micrometry: Micrometry refers to the measurement of dimensions of the desired microorganisms under a microscope which uses two micro- scale known as micrometers . These are two types Types of Micrometry: There are usually two types of micrometers Stage micrometer . Ocular meter or ocular micrometer

4. MICROMETRY Principle Calibration of the ocular micrometer using the stage micrometer

5. OCULAR MICROMETER The ocular micrometer is a glass disc with 100 equal divisions or lines on it but with no absolute value and it is placed in the ocular of the microscope

6. STAGE MICROMETER It is used to calibrate the Ocular micrometer . It looks like a microscope slide but has a standard scale etched into it. The smallest divisions are 0.01mm In length. It is just like a tiny ruler. 0.01mm=10 micro m

7. MICROMETERY Materials Light microscope Ocular micrometer Stage micrometer

8. PROCEDURE The eyepiece is removed from the microscope, and the ocular micrometer is placed carefully into the eyepiece. The eyepiece is placed back in the microscope . The stage micrometer is clipped to the stage and the etchings centered by moving the mechanical stage. The low power objective is taken to position. The eyepiece is rotated till the etchings on both the micrometers superimpose.

9. The required objective is taken to position. The required objective is that, using which the whole microorganism can be viewed and it covers the microscopic field to the maximum possible extent. With the required objective in position the mechanical stage is moved, so that a line on the stage micrometer coincides with a line on the ocular micrometer . Then, another line is searched on the ocular micrometer , which coincides with another line on the stage micrometer . The number of divisions between the coinciding lines is counted for both the micrometers .

10. The calibration factor for the objective used is calculated. The stage micrometer is removed. The slide containing the microbe to be observed is placed on the stage and focused. The number of ocular divisions covered by the microbe is counted by viewing through the eyepiece. The size of the microorganism is determined by multiplying the number of ocular divisions covered by the microbe with the calibration factor.

11. Application: This method is more important in microbiological laboratory. The main purpose of this method to identified the length if the organism such as bacteria, virus, human RBC cells, yeast cell etc..