What you are seeing is pandas truncating the output for display purposes only.
The default max_colwidth
value is 50 which is what you are seeing.
You can set this value to whatever you desire or you can set it to -1 which effectively turns this off:
pd.set_option('display.max_colwidth', -1)
Although I would advise against this, it would be better to set it to something that can be displayed easily in your console or ipython.
A list of the options can be found here: http://pandas.pydata.org/pandas-docs/stable/options.html