Fixed. In case anyone else needs this info, here it is.
As is almost the always the case, this option is documented. From WordPress codex documentation
Modifying How Posts are Displayed
Excerpts vs. Full Posts
Perhaps you are looking to cut down on the size of your Category pages. You could do this by displaying excerpts rather than the entire content of each Post. To do this, you will just need to find where it says the_content() inside The Loop in your Template, and replace it with the_excerpt(). These will most likely be inside PHP tags:
<?php the_excerpt(); ?>
and
<?php the_content(); ?>
