Practical 7

Examining Slides of Blood

In this activity, you will be using a microscope to look at a ‘smear’ of mammalian blood. When blood is smeared onto a microscope slide, it is spread out very thinly so that we can see as much as possible.

Safety

These safety points mainly tell you about hazard. You will need to think about the risk(s) this might pose, and how you can minimize the risk.

• If you use lamps in this activity, you may find that they become hot.

Method

• Set up your microscope as instructed by your teacher. Start off with low magnification, and adjust the focus until you are able to see an image. You will need to angle the mirror so that light is reflected into the microscope (either from a lamp, or light from a window). Note down what you can see at low magnification.
• Now change the magnification to the next level, focus, and note what you see.
• Lastly, use the highest magnification. Focussing is more difficult at this magnification, and you will need to use the fine focussing adjustment. When you can see a clear image, try to draw what you can see.

Discussion

• What can you say about the sizes of the cells in blood?
• What can you say about the number of cells in blood?
• Do all the cells look exactly the same?