You should use a div inside of your table cell to create the desired effect. Making a table cell have a scroll bar doesn't always work.
Here's the code and an example:
<div style="overflow: auto; height: 100px; width: 200px;">Put your text or images or anything in here.</div>
This text is a fixed size because it is inside of a div with style applied to it of style="overflow: auto; height: 100px; width: 200px;"
This text is a fixed size because it is inside of a div with style applied to it of style="overflow: auto; height: 100px; width: 200px;"
Abraham