Microsoft Access forms

In the attached database, I've created a form called fromsearchsample.  This is a forms that allows the user to enter the first name or  last name of an individual in the list, click search and filter out the user.  The form works fine, if I enter just the first name of someone on the list, the form will filter a list of individuals in which choose.  If I double click on the indiividual;s name a form of the individual's information will display.  The problem is if I enter the just the last name of an individual in the last name field, it will not  work correctly.  It does not display any names with the same last name.  Could you please provide the correct code in the form that will allow me to enter a first name only or last name only to perform a search of an individual?  Not first and last name in the field to get results.
NDAlog-2013-09-20-1.accdb